Preserving photon qubits in an unknown quantum state with Knill Dynamical Decoupling - Towards an all optical quantum memory

TL;DR

This paper demonstrates that Knill dynamical decoupling using half-wave plates can effectively preserve photon qubits in unknown quantum states with high fidelity, addressing decoherence in optical quantum communication.

Contribution

It introduces a practical implementation of Knill dynamical decoupling with half-wave plates to maintain quantum state fidelity in optical fibers.

Findings

Achieves >99% fidelity without rotation error

Achieves >96% fidelity with rotation error

Potential for high-fidelity optical quantum memory

Abstract

The implementation of polarization-based quantum communication is limited by signal loss and decoherence caused by the birefringence of a single-mode fiber. We investigate the Knill dynamical decoupling scheme, implemented using half-wave plates, to minimize decoherence and show that a fidelity greater than $99\%$ can be achieved in absence of rotation error and fidelity greater than $96\%$ can be achieved in presence of rotation error. Such a scheme can be used to preserve any quantum state with high fidelity and has potential application for constructing all optical quantum delay line, quantum memory, and quantum repeater.