Faithful quantum state transfer between weakly coupled qubits

TL;DR

This paper presents a probabilistic method for perfect quantum state transfer between weakly coupled qubits, using measurement and filtering, demonstrated experimentally with photons, overcoming interaction limitations.

Contribution

It introduces a novel probabilistic scheme for faithful quantum state transfer between weakly interacting qubits, verified experimentally with linear optics.

Findings

Achieved perfect state transfer probabilistically

Demonstrated robustness against interaction limitations

Validated scheme with photon polarization qubits

Abstract

One of the strengths of quantum information theory is that it can treat quantum states without referring to their particular physical representation. In principle, quantum states can be therefore fully swapped between various quantum systems by their mutual interaction and this quantum state transfer is crucial for many quantum communication and information processing tasks. In practice, however, the achievable interaction time and strength are often limited by decoherence. Here we propose and experimentally demonstrate a procedure for faithful quantum state transfer between two weakly interacting qubits. Our scheme enables a probabilistic yet perfect unidirectional transfer of an arbitrary unknown state of a source qubit onto a target qubit prepared initially in a known state. The transfer is achieved by a combination of a suitable measurement of the source qubit and quantum filtering on the target qubit depending on the outcome of measurement on the source qubit. We experimentally verify feasibility and robustness of the transfer using a linear optical setup with qubits encoded into polarization states of single photons.