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Steindl P, Snijders H, Westra G, Hissink E, Iakovlev K, Polla S, Frey JA, Norman J, Gossard AC, Bowers JE, Bouwmeester D, Löffler W. Artificial Coherent States of Light by Multiphoton Interference in a Single-Photon Stream. PHYSICAL REVIEW LETTERS 2021; 126:143601. [PMID: 33891441 DOI: 10.1103/physrevlett.126.143601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 03/05/2021] [Indexed: 06/12/2023]
Abstract
Coherent optical states consist of a quantum superposition of different photon number (Fock) states, but because they do not form an orthogonal basis, no photon number states can be obtained from it by linear optics. Here we demonstrate the reverse, by manipulating a random continuous single-photon stream using quantum interference in an optical Sagnac loop, we create engineered quantum states of light with tunable photon statistics, including approximate weak coherent states. We demonstrate this experimentally using a true single-photon stream produced by a semiconductor quantum dot in an optical microcavity, and show that we can obtain light with g^{(2)}(0)→1 in agreement with our theory, which can only be explained by quantum interference of at least 3 photons. The produced artificial light states are, however, much more complex than coherent states, containing quantum entanglement of photons, making them a resource for multiphoton entanglement.
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Frey JA, Snijders HJ, Norman J, Gossard AC, Bowers JE, Löffler W, Bouwmeester D. Electro-optic polarization tuning of microcavities with a single quantum dot. OPTICS LETTERS 2018; 43:4280-4283. [PMID: 30160707 DOI: 10.1364/ol.43.004280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 08/12/2018] [Indexed: 06/08/2023]
Abstract
We present an oxide aperture microcavity with embedded quantum dots which utilizes a three-contact design to independently tune the quantum dot wavelength and birefringence of the cavity modes. A polarization splitting tuning of ∼5 GHz is observed. For a typical microcavity polarization splitting, the method can be used to achieve perfect polarization degeneracy that is required for many polarization-based implementations of photonic quantum gates. The embedded quantum dot wavelength can be tuned into resonance with the cavity, independent of the polarization tuning.
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Snijders HJ, Frey JA, Norman J, Flayac H, Savona V, Gossard AC, Bowers JE, van Exter MP, Bouwmeester D, Löffler W. Observation of the Unconventional Photon Blockade. PHYSICAL REVIEW LETTERS 2018; 121:043601. [PMID: 30095925 DOI: 10.1103/physrevlett.121.043601] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Indexed: 06/08/2023]
Abstract
We observe the unconventional photon blockade effect in quantum dot cavity QED, which, in contrast to the conventional photon blockade, operates in the weak coupling regime. A single quantum dot transition is simultaneously coupled to two orthogonally polarized optical cavity modes, and by careful tuning of the input and output state of polarization, the unconventional photon blockade effect is observed. We find a minimum second-order correlation g^{(2)}(0)≈0.37, which corresponds to g^{(2)}(0)≈0.005 when corrected for detector jitter, and observe the expected polarization dependency and photon bunching and antibunching; close by in parameter space, which indicates the abrupt change from phase to amplitude squeezing.
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Kozina M, Trigo M, Chollet M, Clark JN, Glownia JM, Gossard AC, Henighan T, Jiang MP, Lu H, Majumdar A, Zhu D, Reis DA. Heterodyne x-ray diffuse scattering from coherent phonons. Struct Dyn 2017; 4:054305. [PMID: 28852687 PMCID: PMC5552389 DOI: 10.1063/1.4989401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 07/31/2017] [Indexed: 11/30/2022] Open
Abstract
Here, we report Fourier-transform inelastic x-ray scattering measurements of photoexcited GaAs with embedded ErAs nanoparticles. We observe temporal oscillations in the x-ray scattering intensity, which we attribute to inelastic scattering from coherent acoustic phonons. Unlike in thermal equilibrium, where inelastic x-ray scattering is proportional to the phonon occupation, we show that the scattering is proportional to the phonon amplitude for coherent states. The wavevectors of the observed phonons extend beyond the excitation wavevector. The nanoparticles break the discrete translational symmetry of the lattice, enabling the generation of large wavevector coherent phonons. Elastic scattering of x-ray photons from the nanoparticles provides a reference for heterodyne mixing, yielding signals proportional to the phonon amplitude.
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Biesinger DEF, Scheller CP, Braunecker B, Zimmerman J, Gossard AC, Zumbühl DM. Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot. PHYSICAL REVIEW LETTERS 2015; 115:106804. [PMID: 26382695 DOI: 10.1103/physrevlett.115.106804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Indexed: 06/05/2023]
Abstract
We report a thermally activated metastability in a GaAs double quantum dot exhibiting real-time charge switching in diamond shaped regions of the charge stability diagram. Accidental charge traps and sensor backaction are excluded as the origin of the switching. We present an extension of the canonical double dot theory based on an intrinsic, thermal electron exchange process through the reservoirs, giving excellent agreement with the experiment. The electron spin is randomized by the exchange process, thus facilitating fast, gate-controlled spin initialization. At the same time, this process sets an intrinsic upper limit to the spin relaxation time.
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Kuznetsova YY, Andreakou P, Hasling MW, Leonard JR, Calman EV, Butov LV, Hanson M, Gossard AC. Two-dimensional snowflake trap for indirect excitons. OPTICS LETTERS 2015; 40:589-592. [PMID: 25680157 DOI: 10.1364/ol.40.000589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present experimental proof of principle for two-dimensional electrostatic traps for indirect excitons. A confining trap potential for indirect excitons is created by a snowflake-shaped electrode pattern. We demonstrate collection of indirect excitons from all directions to the trap center and control of the trap potential by voltage.
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Yoneda J, Otsuka T, Nakajima T, Takakura T, Obata T, Pioro-Ladrière M, Lu H, Palmstrøm CJ, Gossard AC, Tarucha S. Fast electrical control of single electron spins in quantum dots with vanishing influence from nuclear spins. PHYSICAL REVIEW LETTERS 2014; 113:267601. [PMID: 25615383 DOI: 10.1103/physrevlett.113.267601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Indexed: 06/04/2023]
Abstract
We demonstrate fast universal electrical spin manipulation with inhomogeneous magnetic fields. With fast Rabi frequency up to 127 MHz, we leave the conventional regime of strong nuclear-spin influence and observe a spin-flip fidelity >96%, a distinct chevron Rabi pattern in the spectral-time domain, and a spin resonance linewidth limited by the Rabi frequency, not by the dephasing rate. In addition, we establish fast z rotations up to 54 MHz by directly controlling the spin phase. Our findings will significantly facilitate tomography and error correction with electron spins in quantum dots.
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Higginbotham AP, Kuemmeth F, Hanson MP, Gossard AC, Marcus CM. Coherent operations and screening in multielectron spin qubits. PHYSICAL REVIEW LETTERS 2014; 112:026801. [PMID: 24484035 DOI: 10.1103/physrevlett.112.026801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Indexed: 06/03/2023]
Abstract
Multielectron spin qubits are demonstrated, and performance examined by comparing coherent exchange oscillations in coupled single-electron and multielectron quantum dots, measured in the same device. Fast (>1 GHz) exchange oscillations with a quality factor Q∼15 are found for the multielectron case, compared to Q∼2 for the single-electron case, the latter consistent with experiments in the literature. A model of dephasing that includes voltage and hyperfine noise is developed that is in good agreement with both single- and multielectron data, though in both cases additional exchange-independent dephasing is needed to obtain quantitative agreement across a broad parameter range.
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Bauerschmidt ST, Döhler GH, Lu H, Gossard AC, Malzer S, Preu S. Arrayed free space continuous-wave terahertz photomixers. OPTICS LETTERS 2013; 38:3673-3676. [PMID: 24104843 DOI: 10.1364/ol.38.003673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We present free space coherent arrays of continuous-wave terahertz (THz) photomixers and compare the results to on-chip arrays. By altering the relative phases of the exciting laser signals, the relative THz phase between the array elements can be tuned, allowing for beam steering. In addition, the constructive interference of the emission of N elements leads to an increase of the focal intensity by a factor of N2 while reducing the beam width by ∼N(-1), below the diffraction limit of a single source. Such array architectures strongly improve the THz power distribution for stand-off spectroscopy and imaging systems while providing a huge bandwidth at the same time. We demonstrate this by beam profiles generated by a 2×2 and a 4×1 array for a transmission distance of 4.2 m. Spectra between 70 GHz and 1.1 THz have been recorded with these arrays.
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Medford J, Beil J, Taylor JM, Bartlett SD, Doherty AC, Rashba EI, DiVincenzo DP, Lu H, Gossard AC, Marcus CM. Self-consistent measurement and state tomography of an exchange-only spin qubit. NATURE NANOTECHNOLOGY 2013; 8:654-659. [PMID: 23995458 DOI: 10.1038/nnano.2013.168] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 07/20/2013] [Indexed: 06/02/2023]
Abstract
Quantum-dot spin qubits characteristically use oscillating magnetic or electric fields, or quasi-static Zeeman field gradients, to realize full qubit control. For the case of three confined electrons, exchange interaction between two pairs allows qubit rotation around two axes, hence full control, using only electrostatic gates. Here, we report initialization, full control, and single-shot readout of a three-electron exchange-driven spin qubit. Control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in less than 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements and non-orthogonal control axes.
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Medford J, Beil J, Taylor JM, Rashba EI, Lu H, Gossard AC, Marcus CM. Quantum-dot-based resonant exchange qubit. PHYSICAL REVIEW LETTERS 2013; 111:050501. [PMID: 23952375 DOI: 10.1103/physrevlett.111.050501] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Indexed: 06/02/2023]
Abstract
We introduce a solid-state qubit in which exchange interactions among confined electrons provide both the static longitudinal field and the oscillatory transverse field, allowing rapid and full qubit control via rf gate-voltage pulses. We demonstrate two-axis control at a detuning sweet spot, where leakage due to hyperfine coupling is suppressed by the large exchange gap. A π/2-gate time of 2.5 ns and a coherence time of 19 μs, using multipulse echo, are also demonstrated. Model calculations that include effects of hyperfine noise are in excellent quantitative agreement with experiment.
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Preu S, Mittendorff M, Winnerl S, Lu H, Gossard AC, Weber HB. Ultra-fast transistor-based detectors for precise timing of near infrared and THz signals. OPTICS EXPRESS 2013; 21:17941-17950. [PMID: 23938666 DOI: 10.1364/oe.21.017941] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A whole class of two-color experiments involves intense, short Terahertz radiation pulses. A fast and moderately sensitive detector capable to resolve both near-infrared and Terahertz pulses at the same time is highly desirable. Here we present the first detector of this kind. The detector element is a GaAs-based field effect transistor operated at room temperature. THz detection is successfully demonstrated at frequencies up to 4.9 THz. The THz detection time constant is shorter than 30 ps, the optical time constant is 150 ps. This detector is ideally suited for precise, simultaneous resolution of optical and THz pulses and for pulse characterization of high-power THz pulses up to tens of kW peak power levels. The dynamic range of the detector is as large as 65±3dB/Hz, enabling applications in a large variety of experiments and setups, also including table-top systems.
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High AA, Hammack AT, Leonard JR, Yang S, Butov LV, Ostatnický T, Vladimirova M, Kavokin AV, Liew TCH, Campman KL, Gossard AC. Spin currents in a coherent exciton gas. PHYSICAL REVIEW LETTERS 2013; 110:246403. [PMID: 25165944 DOI: 10.1103/physrevlett.110.246403] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Indexed: 06/03/2023]
Abstract
We report the observation of spin currents in a coherent gas of indirect excitons. The realized long-range spin currents originate from the formation of a coherent gas of bosonic pairs--a new mechanism to suppress the spin relaxation. The spin currents result in the appearance of a variety of polarization patterns, including helical patterns, four-leaf patterns, spiral patterns, bell patterns, and periodic patterns. We demonstrate control of the spin currents by a magnetic field. We also present a theory of coherent exciton spin transport that describes the observed exciton polarization patterns and indicates the trajectories of the spin currents.
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Ribeiro H, Burkard G, Petta JR, Lu H, Gossard AC. Coherent adiabatic spin control in the presence of charge noise using tailored pulses. PHYSICAL REVIEW LETTERS 2013; 110:086804. [PMID: 23473186 DOI: 10.1103/physrevlett.110.086804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Indexed: 06/01/2023]
Abstract
We study finite-time Landau-Zener transitions at a singlet-triplet level crossing in a GaAs double quantum dot, both experimentally and theoretically. Sweeps across the anticrossing in the high driving speed limit result in oscillations with a small visibility. Here we demonstrate how to increase the oscillation visibility while keeping sweep times shorter than T(2)(*) using a tailored pulse with a detuning dependent level velocity. Our results show an improvement of a factor of ~2.9 for the oscillation visibility. In particular, we were able to obtain a visibility of ~0.5 for Stückelberg oscillations, which demonstrates the creation of an equally weighted superposition of the qubit states.
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Colless JI, Mahoney AC, Hornibrook JM, Doherty AC, Lu H, Gossard AC, Reilly DJ. Dispersive readout of a few-electron double quantum dot with fast RF gate sensors. PHYSICAL REVIEW LETTERS 2013; 110:046805. [PMID: 25166190 DOI: 10.1103/physrevlett.110.046805] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Indexed: 06/03/2023]
Abstract
We report the dispersive charge-state readout of a double quantum dot in the few-electron regime using the in situ gate electrodes as sensitive detectors. We benchmark this gate sensing technique against the well established quantum point contact charge detector and find comparable performance with a bandwidth of ∼ 10 MHz and an equivalent charge sensitivity of ∼ 6.3 × 10(-3) e/sqrt[Hz]. Dispersive gate sensing alleviates the burden of separate charge detectors for quantum dot systems and promises to enable readout of qubits in scaled-up arrays.
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High AA, Leonard JR, Remeika M, Butov LV, Hanson M, Gossard AC. Reply to "comment on 'condensation of excitons in a trap'". NANO LETTERS 2012; 12:5422. [PMID: 22978516 DOI: 10.1021/nl302928v] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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High AA, Leonard JR, Remeika M, Butov LV, Hanson M, Gossard AC. Condensation of excitons in a trap. NANO LETTERS 2012; 12:2605-2609. [PMID: 22509898 DOI: 10.1021/nl300983n] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Condensation is observed in a gas of indirect excitons confined in an electrostatic trap. Imaging and interferometric measurements detect that excitons condense at the trap bottom and exciton spontaneous coherence emerges with lowering temperature. Below a temperature of about 1 K, the direct signature of Bose-Einstein condensation, the extension of coherence over the entire cloud, is observed.
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Preu S, Lu H, Sherwin MS, Gossard AC. Detection of nanosecond-scale, high power THz pulses with a field effect transistor. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:053101. [PMID: 22667596 DOI: 10.1063/1.4705986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We demonstrate detection and resolution of high power, 34 ns free electron laser pulses using a rectifying field effect transistor. The detector remains linear up to an input power of 11 ± 0.5 W at a pulse energy of 20 ± 1 μJ at 240 GHz. We compare its performance to a protected Schottky diode, finding a shorter intrinsic time constant. The damage threshold is estimated to be a few 100 W. The detector is, therefore, well-suited for characterizing high power THz pulses. We further demonstrate that the same detector can be used to detect low power continuous-wave THz signals with a post detection limited noise floor of 3.1 μW/√Hz. Such ultrafast, high power detectors are important tools for high power and high energy THz facilities such as free electron lasers.
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High AA, Leonard JR, Hammack AT, Fogler MM, Butov LV, Kavokin AV, Campman KL, Gossard AC. Spontaneous coherence in a cold exciton gas. Nature 2012; 483:584-8. [DOI: 10.1038/nature10903] [Citation(s) in RCA: 231] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 01/17/2012] [Indexed: 11/09/2022]
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Medford J, Cywiński Ł, Barthel C, Marcus CM, Hanson MP, Gossard AC. Scaling of dynamical decoupling for spin qubits. PHYSICAL REVIEW LETTERS 2012; 108:086802. [PMID: 22463554 DOI: 10.1103/physrevlett.108.086802] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Indexed: 05/31/2023]
Abstract
We investigate the scaling of coherence time T(2) with the number of π pulses n(π) in a singlet-triplet spin qubit using Carr-Purcell-Meiboom-Gill (CPMG) and concatenated dynamical decoupling (CDD) pulse sequences. For an even numbers of CPMG pulses, we find a power law T(2) is proportional to (n(π))(γ(e)), with γ(e)=0.72±0.01, essentially independent of the envelope function used to extract T(2). From this surprisingly robust value, a power-law model of the noise spectrum of the environment, S(ω)~ω(-β), yields β=γ(e)/(1-γ(e))=2.6±0.1. Model values for T(2)(n(π)) using β=2.6 for CPMG with both even and odd n(π) up to 32 and CDD orders 3 through 6 compare very well with the experiment.
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Brown ER, Young AC, Bjarnason JE, Zimmerman JD, Gossard AC, Kazemi H. MILLIMETER AND SUB-MILLIMETER WAVE PERFORMANCE OF AN ERAS:INALGAAS SCHOTTKY DIODE COUPLED TO A SINGLE-TURN SQUARE SPIRAL. ACTA ACUST UNITED AC 2011. [DOI: 10.1142/s0129156407004576] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We report the first experimental results for noise-equivalent power (NEP) and noise-equivalent temperature difference (NETD) of single-crystal ErAs:InAlGaAs , zero-bias rectifier diodes coupled to free space quasi-optically in the THz region. At a frequency of 639 GHz, an optical NEP of 4.0×10−12 W / Hz 1/2 is measured with the rectifier coupled to a quasi-plane-wave coherent source through a single-turn square spiral antenna. With a broadband thermal (hot water) source, an NETD of 120 mK is measured from the same device. Antenna radiation patterns at 100 GHz and 639 GHz are also presented.
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van Weperen I, Armstrong BD, Laird EA, Medford J, Marcus CM, Hanson MP, Gossard AC. Charge-state conditional operation of a spin qubit. PHYSICAL REVIEW LETTERS 2011; 107:030506. [PMID: 21838342 DOI: 10.1103/physrevlett.107.030506] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Indexed: 05/31/2023]
Abstract
We report coherent operation of a singlet-triplet qubit controlled by the spatial arrangement of two confined electrons in an adjacent double quantum dot that is electrostatically coupled to the qubit. This four-dot system is the specific device geometry needed for two-qubit operations of a two-electron spin qubit. We extract the strength of the capacitive coupling between qubit and adjacent double quantum dot and show that the present geometry allows fast conditional gate operation, opening pathways toward implementation of a universal set of gates for singlet-triplet spin qubits.
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Winbow AG, Leonard JR, Remeika M, Kuznetsova YY, High AA, Hammack AT, Butov LV, Wilkes J, Guenther AA, Ivanov AL, Hanson M, Gossard AC. Electrostatic conveyer for excitons. PHYSICAL REVIEW LETTERS 2011; 106:196806. [PMID: 21668190 DOI: 10.1103/physrevlett.106.196806] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Indexed: 05/30/2023]
Abstract
We report on the study of indirect excitons in moving lattices-conveyers created by a set of ac voltages applied to the electrodes on the sample surface. The wavelength of this moving lattice is set by the electrode periodicity, the amplitude is controlled by the applied voltage, and the velocity is controlled by the ac frequency. We found the dynamical localization-delocalization transition for excitons in the conveyers and determined its dependence on exciton density and conveyer amplitude and velocity.
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Barthel C, Medford J, Marcus CM, Hanson MP, Gossard AC. Interlaced dynamical decoupling and coherent operation of a singlet-triplet qubit. PHYSICAL REVIEW LETTERS 2010; 105:266808. [PMID: 21231704 DOI: 10.1103/physrevlett.105.266808] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Indexed: 05/30/2023]
Abstract
We experimentally demonstrate coherence recovery of singlet-triplet superpositions by interlacing qubit rotations between Carr-Purcell (CP) echo sequences. We then compare the performance of Hahn, CP, concatenated dynamical decoupling (CDD), and Uhrig dynamical decoupling for singlet recovery. In the present case, where gate noise and drift combined with spatially varying hyperfine coupling contribute significantly to dephasing, and pulses have limited bandwidth, CP and CDD yield comparable results, with T(2)∼80 μs.
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Petersson KD, Petta JR, Lu H, Gossard AC. Quantum coherence in a one-electron semiconductor charge qubit. PHYSICAL REVIEW LETTERS 2010; 105:246804. [PMID: 21231547 DOI: 10.1103/physrevlett.105.246804] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 11/02/2010] [Indexed: 05/27/2023]
Abstract
We study quantum coherence in a semiconductor charge qubit formed from a GaAs double quantum dot containing a single electron. Voltage pulses are applied to depletion gates to drive qubit rotations and noninvasive state readout is achieved using a quantum point contact charge detector. We measure a maximum coherence time of ∼7 ns at the charge degeneracy point, where the qubit level splitting is first-order insensitive to gate voltage fluctuations. We compare measurements of the coherence time as a function of detuning with numerical simulations and predictions from a 1/f noise model.
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