1
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Gu A, Cincio L, Coles PJ. Practical Hamiltonian learning with unitary dynamics and Gibbs states. Nat Commun 2024; 15:312. [PMID: 38191523 PMCID: PMC10774402 DOI: 10.1038/s41467-023-44008-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 11/24/2023] [Indexed: 01/10/2024] Open
Abstract
We study the problem of learning the parameters for the Hamiltonian of a quantum many-body system, given limited access to the system. In this work, we build upon recent approaches to Hamiltonian learning via derivative estimation. We propose a protocol that improves the scaling dependence of prior works, particularly with respect to parameters relating to the structure of the Hamiltonian (e.g., its locality k). Furthermore, by deriving exact bounds on the performance of our protocol, we are able to provide a precise numerical prescription for theoretically optimal settings of hyperparameters in our learning protocol, such as the maximum evolution time (when learning with unitary dynamics) or minimum temperature (when learning with Gibbs states). Thanks to these improvements, our protocol has practical scaling for large problems: we demonstrate this with a numerical simulation of our protocol on an 80-qubit system.
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Affiliation(s)
- Andi Gu
- Department of Physics, University of California, Berkeley, Berkeley, CA, USA.
- Harvard Quantum Initiative, Harvard University, Cambridge, MA, 02138, USA.
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
| | - Lukasz Cincio
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Normal Computing Corporation, New York, NY, USA
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2
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Caro MC, Huang HY, Ezzell N, Gibbs J, Sornborger AT, Cincio L, Coles PJ, Holmes Z. Out-of-distribution generalization for learning quantum dynamics. Nat Commun 2023; 14:3751. [PMID: 37407571 DOI: 10.1038/s41467-023-39381-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 06/09/2023] [Indexed: 07/07/2023] Open
Abstract
Generalization bounds are a critical tool to assess the training data requirements of Quantum Machine Learning (QML). Recent work has established guarantees for in-distribution generalization of quantum neural networks (QNNs), where training and testing data are drawn from the same data distribution. However, there are currently no results on out-of-distribution generalization in QML, where we require a trained model to perform well even on data drawn from a different distribution to the training distribution. Here, we prove out-of-distribution generalization for the task of learning an unknown unitary. In particular, we show that one can learn the action of a unitary on entangled states having trained only product states. Since product states can be prepared using only single-qubit gates, this advances the prospects of learning quantum dynamics on near term quantum hardware, and further opens up new methods for both the classical and quantum compilation of quantum circuits.
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Affiliation(s)
- Matthias C Caro
- Department of Mathematics, Technical University of Munich, Garching, Germany.
- Munich Center for Quantum Science and Technology (MCQST), Munich, Germany.
- Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, Berlin, Germany.
- Institute for Quantum Information and Matter, Caltech, Pasadena, CA, USA.
| | - Hsin-Yuan Huang
- Institute for Quantum Information and Matter, Caltech, Pasadena, CA, USA
- Department of Computing and Mathematical Sciences, Caltech, Pasadena, CA, USA
| | - Nicholas Ezzell
- Information Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA
- Department of Physics & Astronomy, University of Southern California, Los Angeles, CA, USA
| | - Joe Gibbs
- Department of Physics, University of Surrey, Guildford, GU2 7XH, UK
- AWE, Aldermaston, Reading, RG7 4PR, UK
| | | | - Lukasz Cincio
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
- Normal Computing Corporation, New York, NY, USA
| | - Zoë Holmes
- Information Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA
- Institute of Physics, Ecole Polytechnique Fédéderale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
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3
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Larocca M, Ju N, García-Martín D, Coles PJ, Cerezo M. Theory of overparametrization in quantum neural networks. Nat Comput Sci 2023; 3:542-551. [PMID: 38177434 DOI: 10.1038/s43588-023-00467-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 05/12/2023] [Indexed: 01/06/2024]
Abstract
The prospect of achieving quantum advantage with quantum neural networks (QNNs) is exciting. Understanding how QNN properties (for example, the number of parameters M) affect the loss landscape is crucial to designing scalable QNN architectures. Here we rigorously analyze the overparametrization phenomenon in QNNs, defining overparametrization as the regime where the QNN has more than a critical number of parameters Mc allowing it to explore all relevant directions in state space. Our main results show that the dimension of the Lie algebra obtained from the generators of the QNN is an upper bound for Mc, and for the maximal rank that the quantum Fisher information and Hessian matrices can reach. Underparametrized QNNs have spurious local minima in the loss landscape that start disappearing when M ≥ Mc. Thus, the overparametrization onset corresponds to a computational phase transition where the QNN trainability is greatly improved. We then connect the notion of overparametrization to the QNN capacity, so that when a QNN is overparametrized, its capacity achieves its maximum possible value.
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Affiliation(s)
- Martín Larocca
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
- Departamento de Física 'J. J. Giambiagi' and IFIBA, FCEyN, Universidad de Buenos Aires, Buenos Aires, Argentina.
| | - Nathan Ju
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Diego García-Martín
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
- Barcelona Supercomputing Center, Barcelona, Spain
- Instituto de Física Teórica, UAM-CSIC, Madrid, Spain
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Marco Cerezo
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
- Information Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, USA
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4
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Huerta Alderete C, Gordon MH, Sauvage F, Sone A, Sornborger AT, Coles PJ, Cerezo M. Inference-Based Quantum Sensing. Phys Rev Lett 2022; 129:190501. [PMID: 36399750 DOI: 10.1103/physrevlett.129.190501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 09/13/2022] [Accepted: 10/03/2022] [Indexed: 06/16/2023]
Abstract
In a standard quantum sensing (QS) task one aims at estimating an unknown parameter θ, encoded into an n-qubit probe state, via measurements of the system. The success of this task hinges on the ability to correlate changes in the parameter to changes in the system response R(θ) (i.e., changes in the measurement outcomes). For simple cases the form of R(θ) is known, but the same cannot be said for realistic scenarios, as no general closed-form expression exists. In this Letter, we present an inference-based scheme for QS. We show that, for a general class of unitary families of encoding, R(θ) can be fully characterized by only measuring the system response at 2n+1 parameters. This allows us to infer the value of an unknown parameter given the measured response, as well as to determine the sensitivity of the scheme, which characterizes its overall performance. We show that inference error is, with high probability, smaller than δ, if one measures the system response with a number of shots that scales only as Ω(log^{3}(n)/δ^{2}). Furthermore, the framework presented can be broadly applied as it remains valid for arbitrary probe states and measurement schemes, and, even holds in the presence of quantum noise. We also discuss how to extend our results beyond unitary families. Finally, to showcase our method we implement it for a QS task on real quantum hardware, and in numerical simulations.
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Affiliation(s)
- C Huerta Alderete
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Quantum Science Center, Oak Ridge, Tennessee 37931, USA
| | - Max Hunter Gordon
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Instituto de Física Teórica, UAM/CSIC, Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Frédéric Sauvage
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Akira Sone
- Aliro Technologies, Inc, Boston, Massachusetts 02135, USA
| | - Andrew T Sornborger
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Quantum Science Center, Oak Ridge, Tennessee 37931, USA
| | - Patrick J Coles
- Quantum Science Center, Oak Ridge, Tennessee 37931, USA
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - M Cerezo
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Quantum Science Center, Oak Ridge, Tennessee 37931, USA
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5
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Cerezo M, Verdon G, Huang HY, Cincio L, Coles PJ. Challenges and opportunities in quantum machine learning. Nat Comput Sci 2022; 2:567-576. [PMID: 38177473 DOI: 10.1038/s43588-022-00311-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 08/04/2022] [Indexed: 01/06/2024]
Abstract
At the intersection of machine learning and quantum computing, quantum machine learning has the potential of accelerating data analysis, especially for quantum data, with applications for quantum materials, biochemistry and high-energy physics. Nevertheless, challenges remain regarding the trainability of quantum machine learning models. Here we review current methods and applications for quantum machine learning. We highlight differences between quantum and classical machine learning, with a focus on quantum neural networks and quantum deep learning. Finally, we discuss opportunities for quantum advantage with quantum machine learning.
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Affiliation(s)
- M Cerezo
- Information Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, USA
- Quantum Science Center, Oak Ridge, TN, USA
| | - Guillaume Verdon
- X, Mountain View, CA, USA
- Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Hsin-Yuan Huang
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA, USA
- Department of Computing and Mathematical Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Lukasz Cincio
- Quantum Science Center, Oak Ridge, TN, USA
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Patrick J Coles
- Quantum Science Center, Oak Ridge, TN, USA.
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
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6
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Caro MC, Huang HY, Cerezo M, Sharma K, Sornborger A, Cincio L, Coles PJ. Generalization in quantum machine learning from few training data. Nat Commun 2022; 13:4919. [PMID: 35995777 PMCID: PMC9395350 DOI: 10.1038/s41467-022-32550-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 08/04/2022] [Indexed: 11/19/2022] Open
Abstract
Modern quantum machine learning (QML) methods involve variationally optimizing a parameterized quantum circuit on a training data set, and subsequently making predictions on a testing data set (i.e., generalizing). In this work, we provide a comprehensive study of generalization performance in QML after training on a limited number N of training data points. We show that the generalization error of a quantum machine learning model with T trainable gates scales at worst as [Formula: see text]. When only K ≪ T gates have undergone substantial change in the optimization process, we prove that the generalization error improves to [Formula: see text]. Our results imply that the compiling of unitaries into a polynomial number of native gates, a crucial application for the quantum computing industry that typically uses exponential-size training data, can be sped up significantly. We also show that classification of quantum states across a phase transition with a quantum convolutional neural network requires only a very small training data set. Other potential applications include learning quantum error correcting codes or quantum dynamical simulation. Our work injects new hope into the field of QML, as good generalization is guaranteed from few training data.
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Affiliation(s)
- Matthias C Caro
- Department of Mathematics, Technical University of Munich, Garching, Germany.
- Munich Center for Quantum Science and Technology (MCQST), Munich, Germany.
| | - Hsin-Yuan Huang
- Institute for Quantum Information and Matter, Caltech, Pasadena, CA, USA
- Department of Computing and Mathematical Sciences, Caltech, Pasadena, CA, USA
| | - M Cerezo
- Information Sciences, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Kunal Sharma
- Joint Center for Quantum Information and Computer Science, University of Maryland, College Park, MD, 20742, USA
| | - Andrew Sornborger
- Information Sciences, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Quantum Science Center, Oak Ridge, TN, 37931, USA
| | - Lukasz Cincio
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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7
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Sharma K, Cerezo M, Cincio L, Coles PJ. Trainability of Dissipative Perceptron-Based Quantum Neural Networks. Phys Rev Lett 2022; 128:180505. [PMID: 35594093 DOI: 10.1103/physrevlett.128.180505] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/22/2021] [Accepted: 04/06/2022] [Indexed: 06/15/2023]
Abstract
Several architectures have been proposed for quantum neural networks (QNNs), with the goal of efficiently performing machine learning tasks on quantum data. Rigorous scaling results are urgently needed for specific QNN constructions to understand which, if any, will be trainable at a large scale. Here, we analyze the gradient scaling (and hence the trainability) for a recently proposed architecture that we call dissipative QNNs (DQNNs), where the input qubits of each layer are discarded at the layer's output. We find that DQNNs can exhibit barren plateaus, i.e., gradients that vanish exponentially in the number of qubits. Moreover, we provide quantitative bounds on the scaling of the gradient for DQNNs under different conditions, such as different cost functions and circuit depths, and show that trainability is not always guaranteed. Our work represents the first rigorous analysis of the scalability of a perceptron-based QNN.
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Affiliation(s)
- Kunal Sharma
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Hearne Institute for Theoretical Physics and Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - M Cerezo
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Lukasz Cincio
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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8
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Geller MR, Arrasmith A, Holmes Z, Yan B, Coles PJ, Sornborger A. Quantum simulation of operator spreading in the chaotic Ising model. Phys Rev E 2022; 105:035302. [PMID: 35428080 DOI: 10.1103/physreve.105.035302] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
There is great interest in using near-term quantum computers to simulate and study foundational problems in quantum mechanics and quantum information science, such as the scrambling measured by an out-of-time-ordered correlator (OTOC). Here we use an IBM Q processor, quantum error mitigation, and weaved Trotter simulation to study high-resolution operator spreading in a four-spin Ising model as a function of space, time, and integrability. Reaching four spins while retaining high circuit fidelity is made possible by the use of a physically motivated fixed-node variant of the OTOC, allowing scrambling to be estimated without overhead. We find clear signatures of a ballistic operator spreading in a chaotic regime, as well as operator localization in an integrable regime. The techniques developed and demonstrated here open up the possibility of using cloud-based quantum computers to study and visualize scrambling phenomena, as well as quantum information dynamics more generally.
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Affiliation(s)
- Michael R Geller
- Center for Simulational Physics, University of Georgia, Athens, Georgia 30602, USA
| | - Andrew Arrasmith
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Zoë Holmes
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Bin Yan
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Andrew Sornborger
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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9
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Sharma K, Cerezo M, Holmes Z, Cincio L, Sornborger A, Coles PJ. Reformulation of the No-Free-Lunch Theorem for Entangled Datasets. Phys Rev Lett 2022; 128:070501. [PMID: 35244415 DOI: 10.1103/physrevlett.128.070501] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 01/19/2022] [Indexed: 06/14/2023]
Abstract
The no-free-lunch (NFL) theorem is a celebrated result in learning theory that limits one's ability to learn a function with a training dataset. With the recent rise of quantum machine learning, it is natural to ask whether there is a quantum analog of the NFL theorem, which would restrict a quantum computer's ability to learn a unitary process with quantum training data. However, in the quantum setting, the training data can possess entanglement, a strong correlation with no classical analog. In this Letter, we show that entangled datasets lead to an apparent violation of the (classical) NFL theorem. This motivates a reformulation that accounts for the degree of entanglement in the training set. As our main result, we prove a quantum NFL theorem whereby the fundamental limit on the learnability of a unitary is reduced by entanglement. We employ Rigetti's quantum computer to test both the classical and quantum NFL theorems. Our Letter establishes that entanglement is a commodity in quantum machine learning.
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Affiliation(s)
- Kunal Sharma
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Hearne Institute for Theoretical Physics and Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - M Cerezo
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Zoë Holmes
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Lukasz Cincio
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Andrew Sornborger
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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10
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Wang S, Fontana E, Cerezo M, Sharma K, Sone A, Cincio L, Coles PJ. Noise-induced barren plateaus in variational quantum algorithms. Nat Commun 2021; 12:6961. [PMID: 34845216 PMCID: PMC8630047 DOI: 10.1038/s41467-021-27045-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 11/01/2021] [Indexed: 11/20/2022] Open
Abstract
Variational Quantum Algorithms (VQAs) may be a path to quantum advantage on Noisy Intermediate-Scale Quantum (NISQ) computers. A natural question is whether noise on NISQ devices places fundamental limitations on VQA performance. We rigorously prove a serious limitation for noisy VQAs, in that the noise causes the training landscape to have a barren plateau (i.e., vanishing gradient). Specifically, for the local Pauli noise considered, we prove that the gradient vanishes exponentially in the number of qubits n if the depth of the ansatz grows linearly with n. These noise-induced barren plateaus (NIBPs) are conceptually different from noise-free barren plateaus, which are linked to random parameter initialization. Our result is formulated for a generic ansatz that includes as special cases the Quantum Alternating Operator Ansatz and the Unitary Coupled Cluster Ansatz, among others. For the former, our numerical heuristics demonstrate the NIBP phenomenon for a realistic hardware noise model.
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Affiliation(s)
- Samson Wang
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
- Imperial College London, London, UK.
| | - Enrico Fontana
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- University of Strathclyde, Glasgow, UK
- National Physical Laboratory, Teddington, UK
| | - M Cerezo
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, USA.
| | - Kunal Sharma
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Hearne Institute for Theoretical Physics and Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, USA
- Joint Center for Quantum Information and Computer Science, University of Maryland, College Park, Maryland, MD, USA
| | - Akira Sone
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, USA
- Aliro Technologies, Inc, Boston, MA, 02135, USA
| | - Lukasz Cincio
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
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11
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Beckey JL, Gigena N, Coles PJ, Cerezo M. Computable and Operationally Meaningful Multipartite Entanglement Measures. Phys Rev Lett 2021; 127:140501. [PMID: 34652179 DOI: 10.1103/physrevlett.127.140501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 08/12/2021] [Indexed: 06/13/2023]
Abstract
Multipartite entanglement is an essential resource for quantum communication, quantum computing, quantum sensing, and quantum networks. The utility of a quantum state |ψ⟩ for these applications is often directly related to the degree or type of entanglement present in |ψ⟩. Therefore, efficiently quantifying and characterizing multipartite entanglement is of paramount importance. In this work, we introduce a family of multipartite entanglement measures, called concentratable entanglements. Several well-known entanglement measures are recovered as special cases of our family of measures, and hence we provide a general framework for quantifying multipartite entanglement. We prove that the entire family does not increase, on average, under local operations and classical communications. We also provide an operational meaning for these measures in terms of probabilistic concentration of entanglement into Bell pairs. Finally, we show that these quantities can be efficiently estimated on a quantum computer by implementing a parallelized SWAP test, opening up a research direction for measuring multipartite entanglement on quantum devices.
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Affiliation(s)
- Jacob L Beckey
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- JILA, NIST and University of Colorado, Boulder, Colorado 80309, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
- Quantum Science Center, Oak Ridge, Tennessee 37931, USA
| | - N Gigena
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Quantum Science Center, Oak Ridge, Tennessee 37931, USA
| | - M Cerezo
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Quantum Science Center, Oak Ridge, Tennessee 37931, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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12
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Affiliation(s)
- Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
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13
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Holmes Z, Arrasmith A, Yan B, Coles PJ, Albrecht A, Sornborger AT. Barren Plateaus Preclude Learning Scramblers. Phys Rev Lett 2021; 126:190501. [PMID: 34047576 DOI: 10.1103/physrevlett.126.190501] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 04/07/2021] [Indexed: 06/12/2023]
Abstract
Scrambling processes, which rapidly spread entanglement through many-body quantum systems, are difficult to investigate using standard techniques, but are relevant to quantum chaos and thermalization. In this Letter, we ask if quantum machine learning (QML) could be used to investigate such processes. We prove a no-go theorem for learning an unknown scrambling process with QML, showing that it is highly probable for any variational Ansatz to have a barren plateau landscape, i.e., cost gradients that vanish exponentially in the system size. This implies that the required resources scale exponentially even when strategies to avoid such scaling (e.g., from Ansatz-based barren plateaus or no-free-lunch theorems) are employed. Furthermore, we numerically and analytically extend our results to approximate scramblers. Hence, our work places generic limits on the learnability of unitaries when lacking prior information.
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Affiliation(s)
- Zoë Holmes
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Andrew Arrasmith
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Bin Yan
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Andreas Albrecht
- Center for Quantum Mathematics and Physics and Department of Physics and Astronomy University of California, Davis, One Shields Ave, Davis, California 95616, USA
| | - Andrew T Sornborger
- Information Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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14
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Cerezo M, Sone A, Volkoff T, Cincio L, Coles PJ. Cost function dependent barren plateaus in shallow parametrized quantum circuits. Nat Commun 2021; 12:1791. [PMID: 33741913 PMCID: PMC7979934 DOI: 10.1038/s41467-021-21728-w] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 02/05/2021] [Indexed: 11/09/2022] Open
Abstract
Variational quantum algorithms (VQAs) optimize the parameters θ of a parametrized quantum circuit V(θ) to minimize a cost function C. While VQAs may enable practical applications of noisy quantum computers, they are nevertheless heuristic methods with unproven scaling. Here, we rigorously prove two results, assuming V(θ) is an alternating layered ansatz composed of blocks forming local 2-designs. Our first result states that defining C in terms of global observables leads to exponentially vanishing gradients (i.e., barren plateaus) even when V(θ) is shallow. Hence, several VQAs in the literature must revise their proposed costs. On the other hand, our second result states that defining C with local observables leads to at worst a polynomially vanishing gradient, so long as the depth of V(θ) is [Formula: see text]. Our results establish a connection between locality and trainability. We illustrate these ideas with large-scale simulations, up to 100 qubits, of a quantum autoencoder implementation.
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Affiliation(s)
- M Cerezo
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, USA.
| | - Akira Sone
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Tyler Volkoff
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Lukasz Cincio
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
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15
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Arrasmith A, Cincio L, Sornborger AT, Zurek WH, Coles PJ. Variational consistent histories as a hybrid algorithm for quantum foundations. Nat Commun 2019; 10:3438. [PMID: 31366888 PMCID: PMC6668436 DOI: 10.1038/s41467-019-11417-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 07/12/2019] [Indexed: 01/07/2023] Open
Abstract
Although quantum computers are predicted to have many commercial applications, less attention has been given to their potential for resolving foundational issues in quantum mechanics. Here we focus on quantum computers’ utility for the Consistent Histories formalism, which has previously been employed to study quantum cosmology, quantum paradoxes, and the quantum-to-classical transition. We present a variational hybrid quantum-classical algorithm for finding consistent histories, which should revitalize interest in this formalism by allowing classically impossible calculations to be performed. In our algorithm, the quantum computer evaluates the decoherence functional (with exponential speedup in both the number of qubits and the number of times in the history) and a classical optimizer adjusts the history parameters to improve consistency. We implement our algorithm on a cloud quantum computer to find consistent histories for a spin in a magnetic field and on a simulator to observe the emergence of classicality for a chiral molecule. The Consistent Histories formalism can solve paradoxes in quantum mechanics, but finding such consistent sets of histories requires a computational overhead which is exponential in the problem’s size. Here, the authors report a variational hybrid algorithm solving this problem using polynomial resources.
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Affiliation(s)
- Andrew Arrasmith
- Theoretical Division, MS 213, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.,Department of Physics, University of California Davis, Davis, CA, 95616, USA
| | - Lukasz Cincio
- Theoretical Division, MS 213, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Andrew T Sornborger
- Information Sciences, MS 256, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Wojciech H Zurek
- Theoretical Division, MS 213, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Patrick J Coles
- Theoretical Division, MS 213, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
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16
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Abstract
Energy-time uncertainty plays an important role in quantum foundations and technologies, and it was even discussed by the founders of quantum mechanics. However, standard approaches (e.g., Robertson's uncertainty relation) do not apply to energy-time uncertainty because, in general, there is no Hermitian operator associated with time. Following previous approaches, we quantify time uncertainty by how well one can read off the time from a quantum clock. We then use entropy to quantify the information-theoretic distinguishability of the various time states of the clock. Our main result is an entropic energy-time uncertainty relation for general time-independent Hamiltonians, stated for both the discrete-time and continuous-time cases. Our uncertainty relation is strong, in the sense that it allows for a quantum memory to help reduce the uncertainty, and this formulation leads us to reinterpret it as a bound on the relative entropy of asymmetry. Because of the operational relevance of entropy, we anticipate that our uncertainty relation will have information-processing applications.
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Affiliation(s)
- Patrick J Coles
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Vishal Katariya
- Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Seth Lloyd
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Iman Marvian
- Departments of Physics & Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, USA
| | - Mark M Wilde
- Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
- Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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17
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Abstract
Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with symmetries, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. Here we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study 'unstructured' protocols, that is, those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which markedly reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown.
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Affiliation(s)
- Patrick J. Coles
- Department of Physics and Astronomy, Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada N2L3G1
| | - Eric M. Metodiev
- Department of Physics and Astronomy, Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada N2L3G1
| | - Norbert Lütkenhaus
- Department of Physics and Astronomy, Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada N2L3G1
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18
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Abstract
Uncertainty relations provide constraints on how well the outcomes of incompatible measurements can be predicted, and as well as being fundamental to our understanding of quantum theory, they have practical applications such as for cryptography and witnessing entanglement. Here we shed new light on the entropic form of these relations, showing that they follow from a few simple properties, including the data-processing inequality. We prove these relations without relying on the exact expression for the entropy, and hence show that a single technique applies to several entropic quantities, including the von Neumann entropy, min- and max-entropies, and the Rényi entropies.
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Affiliation(s)
- Patrick J Coles
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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19
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Abstract
Peptidyl (acyloxy)methyl ketones, previously established as potent irreversible inhibitors of the cysteine proteinase cathepsin B in vitro, were investigated and optimized for their inhibitory activity in vivo. Incorporation of polar or charged functional groups in the inhibitor structure afforded effective cathepsin B inhibition, following dosing to rats. The most effective inhibitor, Z-Phe-Lys-CH2OCO-(2,4,6-Me3)Ph (8), was found to give ED50 values of 18 mg/kg po (orally) and 5.0 mg/kg ip (intraperitoneally) at 4-5 h postdose, and 2.4 mg/kg sc (subcutaneously) at 24 h postdose, for liver cathepsin B inhibition (measured ex vivo). The subcutaneous route of administration of (acyloxy)methyl ketone 8 also provided potent cathepsin B inhibition in certain peripheral tissues (e.g., ED50 1.0 mg/kg for skeletal muscle, 0.1 mg/kg for heart). These investigations demonstrate that peptidyl (acyloxy)methyl ketones such as 8 have promise as tools for the characterization of in vivo biochemical processes and as therapeutic agents.
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Affiliation(s)
- B M Wagner
- Department of Lipid and Protease Biochemistry, Syntex Research, Palo Alto, California 94304
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20
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Brömme D, Smith RA, Coles PJ, Kirschke H, Storer AC, Krantz A. Potent inactivation of cathepsins S and L by peptidyl (acyloxy)methyl ketones. Biol Chem Hoppe Seyler 1994; 375:343-7. [PMID: 8074807 DOI: 10.1515/bchm3.1994.375.5.343] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Peptidyl (acyloxy)methyl ketones (Z-Aa-Aa-CH2-O-CO-R), a new class of irreversible inhibitors whose chemical reactivity can be modulated by varying the substitution pattern of the carboxylate leaving group, are shown to be extremely potent inactivators of the lysosomal cysteine proteinases cathepsin L and cathepsin S. The highest k2/Ki values measured were found to exceed 10(6) M-1s-1 for both cathepsin L and cathepsin S. The rate of inactivation can be controlled by varying the dipeptidyl moiety or the carboxylate leaving group, with the second-order rate constants for both enzymes found to be strongly dependent on the pKa values of the leaving group. The specificities of the cathepsins S and L reveal a different selectivity towards the nature of substitution of the aryl P' leaving group of the inhibitor. This new inhibitor class opens the possibility of the design of selective and specific inhibitors for lysosomal cysteine proteinases.
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Affiliation(s)
- D Brömme
- Molecular Biology Sector, Biotechnology Research Institute, National Research Council of Canada
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21
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Pliura DH, Bonaventura BJ, Smith RA, Coles PJ, Krantz A. Comparative behaviour of calpain and cathepsin B toward peptidyl acyloxymethyl ketones, sulphonium methyl ketones and other potential inhibitors of cysteine proteinases. Biochem J 1992; 288 ( Pt 3):759-62. [PMID: 1471990 PMCID: PMC1131951 DOI: 10.1042/bj2880759] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Peptidyl acyloxymethyl ketones, previously established as potent inactivators of the lysosomal cysteine proteinase cathepsin B, were evaluated against smooth-muscle calpain, a member of the family of Ca(2+)-dependent cysteine proteinases. Only modest rates of time-dependent inhibition could be achieved, even with peptidyl affinity groups optimized for calpain and linked to a carboxylate leaving group of very low pKa [2,6-(CF3)2PhCOO-, pKa 0.58]. Selective inactivation of cathespin B versus calpain was consistently observed with this type of inhibitor. Examination of other potential inhibitors revealed a rank order of potency against calpain to be: peptidyl sulphonium methyl ketones > fluoromethyl ketones, diazomethyl ketones >> acyloxymethyl ketones, an order which differs sharply from that found for cathespin B.
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Affiliation(s)
- D H Pliura
- Syntex Research, Mississauga, Ontario, Canada
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22
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Krantz A, Copp LJ, Coles PJ, Smith RA, Heard SB. Peptidyl (acyloxy)methyl ketones and the quiescent affinity label concept: the departing group as a variable structural element in the design of inactivators of cysteine proteinases. Biochemistry 1991; 30:4678-87. [PMID: 2029515 DOI: 10.1021/bi00233a007] [Citation(s) in RCA: 121] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
(Acyloxy)methyl ketones, of general structure Z-[AA2]-[AA1]-CH2OCOAr, are potent inactivators of the cysteine proteinase cathepsin B. These reagents have been designed as affinity labels in which the dipeptidyl moiety serves as an affinity group (complementary to the S1 and S2 sites of the enzyme), while the (acyloxy)methyl ketone unit (-COCH2OCOR), containing a weak leaving group in the form of a carboxylate nucleofuge, functions as the potentially reactive entity that labels the enzyme. The inhibition is time dependent, active site directed, and irreversible. The apparent second-order rate constant kinact/Kinact, which characterizes the inhibition of cathepsin B by this series, spans several orders of magnitude and in certain cases exceeds 10(6) M-1 s-1. The activity of this series of inhibitors was found to be exquisitely sensitive to the nature of the carboxylate leaving group as well as the affinity group. A strong dependence of second-order inactivation rate on leaving group pKa was uncovered for Z-Phe-Ala (acyloxy)methyl ketones [log(k/K) = 1.1 (+/- 0.1) X pKa + 7.2 (+/- 0.4); r2 = 0.82, n = 26]. Heretofore in constructing affinity labels the choice of leaving group was quite restricted. The aryl carboxylate group thus offers considerable variation as a design element in that both its binding affinity and reactivity can be controlled by substituent effects. Specific peptidyl (acyloxy)methyl ketones thus represent prime examples of highly potent, chemically stable enzyme inhibitors with variable structural elements in both the affinity and departing groups.
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Affiliation(s)
- A Krantz
- Syntex Research, Mississauga, Ontario, Canada
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23
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Abstract
Peptidyl O-acyl hydroxamates having appropriate active-site recognition features are very potent time-dependent inhibitors of the cysteine proteinase cathepsin B. The inhibition is irreversible, and the inactivation rate is strongly dependent on peptide structure and correct positioning of the P1 amino acid carbonyl group. Lipophilic O-acyl groups provide the most rapid inactivators, as exemplified by the inhibitor O-mesitoyl N-benzyloxycarbonyl-L-phenylalanyl-L-alanine hydroxamate (kmax/Ki = 640,000 M-1s-1).
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Affiliation(s)
- R A Smith
- Syntex Research, Mississauga, Ontario, Canada
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