Quantum tele-amplification with a continuous-variable superposition state

Abstract

Optical coherent states are classical light fields with high purity, and are essential carriers of information in optical networks. If these states could be controlled in the quantum regime, allowing for their quantum superposition (referred to as a Schrödinger cat state), then novel quantumenhanced functions such as coherent-state quantum computing (CSQC) 1-5 , quantum metrology 6,7 , and a quantum repeater 8,9 , could be realized in the networks. Optical cat states are now routinely generated in the laboratories. An important next challenge is to use them for implementing the aforementioned functions. Here we demonstrate a basic CSQC protocol, where a cat state is used as an entanglement resource for teleporting a coherent state with an amplitude gain. We also show how this can be extended to a loss-tolerant quantum relay of multi-ary phase-shift keyed coherent states. These protocols could be useful both in optical and quantum communications. arXiv:1211.6634v2 [quant-ph]

Bell-inequality tests using asymmetric entangled coherent states in asymmetric lossy environments

“…5 to have the smaller amplitude). Such a strategy was also applied to the tele-amplification protocol [48] and the distributed generation scheme for ECSs [49]. .…”

“…An ECS in a free-traveling field was experimentally generated using the photon subtraction technique on two approximate superpositions of coherent states (SCSs) [47]. A proof-of-principle demonstration of quantum teleportation using an ECS as a quantum channel was performed [48].…”

Purification of photon subtraction from continuous squeezed light by filtering

“…The amplitude of cat states can be enlarged with conditional methods [4,11]. Cat states are resources for teleamplification of coherent states [12]. Hybridization of coherent-state qubits and number-state qubits is also demonstrated [13,14].…”

Generating non-classical states from spin coherent states via interaction with ancillary spins

“…Recently, continuous-variable (CV) superposed/entangled states have shown their potential in various optical and photonic experiments [6] and the use of CV entangled states can be robust in practical quantum metrology [7,8,9].…”