Efficient and perfect state transfer in quantum chains

Well-protected quantum state transfer in a dissipative spin chain

In this work, a mechanism is investigated for improving the quantum state transfer efficiency in a spin chain, which is in contact with a dissipative structured reservoir. The efficiency of the method is based on the addition of similar non-interacting auxiliary chains into the reservoir. In this way, we obtain the exact solution for the master equation of the spin chain in the presence of dissipation. It is found out that entering more auxiliary chains into the reservoir causes, in general, the better improvement of the fidelity of state transfer along the mentioned chain. Furthermore, it is reveal that the protocol has better efficiency for a chain with longer length. Therefore, by this method, quantum state transfer along a linear chain with an arbitrary number of qubits, can be well-protected against the dissipative noises.

Experimental perfect state transfer of an entangled photonic qubit

The transfer of data is a fundamental task in information systems. Microprocessors contain dedicated data buses that transmit bits across different locations and implement sophisticated routing protocols. Transferring quantum information with high fidelity is a challenging task, due to the intrinsic fragility of quantum states. Here we report on the implementation of the perfect state transfer protocol applied to a photonic qubit entangled with another qubit at a different location. On a single device we perform three routing procedures on entangled states, preserving the encoded quantum state with an average fidelity of 97.1%, measuring in the coincidence basis. Our protocol extends the regular perfect state transfer by maintaining quantum information encoded in the polarization state of the photonic qubit. Our results demonstrate the key principle of perfect state transfer, opening a route towards data transfer for quantum computing systems.

Transferring quantum information is a fundamental task, but doing so with high fidelity is a challenging task. Here, the authors implement the perfect state transfer protocol to a photonic qubit, entangled with a second one in a different location, across eleven coupled waveguides.

Mirror Inverse Operations in Linear Nearest Neighbors Using Dynamic Learning Algorithm

We propose a new method to implement mirror inverse gate operations in 1-D linear nearest neighbor (LNN) array coupled through diagonal interactions, using a dynamic learning algorithm. This is accomplished by training a quantum system using a backpropagation technique, to find the parameters of the system Hamiltonian that implement the mirror inverse operation. We show how the training algorithm can be used as a tool for finding the parameters for implementing mirror inverse operations in LNN systems with increasing number of qubits. The key feature of our scheme is that once we find the system parameters using the learning algorithm, mirror inversion (MI) is accomplished simply by tuning the system parameters to these values and allowing the system to evolve for a chosen time interval. To validate our scheme, we compare our results against known results for an LNN system coupled through XY interactions. We also show how the scheme can be used to implement MI operations in the presence of unwanted couplings.

Quantum communication beyond the localization length in disordered spin chains

We study the effects of localization on quantum state transfer in spin chains. We show how to use quantum error correction and multiple parallel spin chains to send a qubit with high fidelity over arbitrary distances, in particular, distances much greater than the localization length of the chain.

Improved transfer of quantum information using a local memory

We demonstrate that the quantum communication between two parties can be significantly improved if the receiver is allowed to store the received signals in a quantum memory before decoding them. In the limit of an infinite memory, the transfer is perfect. We prove that this scheme allows the transfer of arbitrary multipartite states along Heisenberg chains of spin-1/2 particles with random coupling strengths.