State transformation in photon-echo quantum memory

TL;DR

This paper explores photon-echo interactions in quantum memory to enable both storage and controlled quantum state transformations, demonstrated through unambiguous state discrimination of qubits and qutrits in a solid-state system.

Contribution

It introduces a method to combine quantum state storage with controlled transformations using photon-echo interactions in a solid-state waveguide.

Findings

Successful demonstration of unambiguous state discrimination of qubits and qutrits.

High robustness and flexibility of the photon-echo based approach.

Potential applications in quantum communication, computation, and precision measurements.

Abstract

Quantum memory is a key element for quantum repeaters and linear optical quantum computers. In addition to memory, repeaters and computers also require manipulating quantum states by means of unitary transformations, which is generally accomplished using interferometric optical setups. We experimentally investigate photon-echo type atom-light interaction for the possibility to combine storage with controlled transformation of quantum states. As an example, we demonstrate unambiguous state discrimination of qubits and qutrits in an Ti:Er:LiNbO$_3$ waveguide cooled to 3K using states encoded into large ensembles of identically prepared photons in superposition of different temporal modes. The high robustness and flexibility of our approach makes it promising for quantum communication and computation as well as precision measurements.