Directly comparing entanglement-enhancing non-Gaussian operations

Abstract

Single-photon-level non-Gaussian operations-photon addition, photon subtraction, and their coherent superposition-are powerful tools with which to increase entanglement in continuous-variable optical states. Although such operations are typically not deterministic, there may be other advantages such as noiseless manipulation. Therefore, to fully account for the efficacy of a particular non-Gaussian operation in a practical scenario, we develop figures of merit which trade off the advantages of such protocols against their success probability. Specifically, we define 'entanglement enhancement rate' as the increase in entanglement per trial of a generic non-Gaussian operation on a two-mode squeezed vacuum (TMSV) state. We consider states generated by photon-subtraction, photon-addition and a coherent superposition of subtraction and addition. We compare each strategy when applied to one or both modes of a TMSV state, and also in the presence of channel losses prior to the operation. In many cases, additional properties are analytically calculable, including excess noise arising from the operation and the fidelity of the resulting states to particular Gaussian and non-Gaussian states. Finally, by incorporating loss, we derive optimal interaction parameters for each non-Gaussian operation which maximize the effectiveness of the particular protocol under investigation.

Quantum Entanglement Distribution Innext-Generation Wireless Communication Systems

“…A PSS state is created from the incoming TMSV state (with squeezing r) by subtracting one photon from each mode (using beam splitters with the same transmissivity κ). In terms of the Fock state |n such a non-Gaussian state is given by (e.g., [21]) |P SS = ∞ n=0 q n |n 1 |n 2 ,…”

Non-Gaussian and Gottesman–Kitaev–Preskill state preparation by photon catalysis

“…By varying the parameters of the beamsplitter, Bartley et al experimentally performed single-photon catalysis on a coherent state input to demonstrate the creation of states exhibiting nonclassical photon statistics. Photon catalysis has also been explored in utilizing multi photon detection [33], with general single-mode Gaussian inputs [34], and for use as an entanglement enhancer [35]. Note that near-unity efficiency PNR is now an experimentally available resource, thanks to superconducting transition-edge sensors [36].…”

CV-QKD with Gaussian and Non-Gaussian Entangled States over Satellite-Based Channels

“…[10]- [13]. Such studies can be motivated in part by the fact that non-Gaussian operations such as photon subtraction [14]- [21] and photon addition [16], [19], [21]- [23] on an incoming TMSV state can lead to higher levels of entanglement [19].…”