Algorithm of quantum engineering of large-amplitude high-fidelity cat states in setup with k beam splitters and with inefficient photon number resolving detection

TL;DR

This paper introduces an algorithm for generating large-amplitude, high-fidelity Schrödinger cat states using a setup with multiple beam splitters and photon number resolving detectors, improving success probability and reducing detector requirements.

Contribution

The authors propose a novel quantum engineering scheme employing multiple beam splitters and multiphoton splitting to enhance success probability and relax detector efficiency constraints in cat state generation.

Findings

Multiphoton splitting increases success probability compared to single detector schemes.

Fidelity and success probability are in conflict, especially with inefficient detectors.

Using up to 20 photon subtractions yields high-fidelity cat states with acceptable success rates.

Abstract

We present an algorithm of quantum engineering of large-amplitude>5 high-fidelity>0.99 even/odd Schrodinger cat states (SCSs) using a single mode squeezed vacuum (SMSV) state as resource. Set of k beam splitters (BSs) with arbitrary transmittance and reflectance coefficients sequentially following each other acts as a hub that redirects a multiphoton state into the measuring modes simultaneously measured by photon number resolving (PNR) detectors. We show that the multiphoton state splitting guarantees significant increase of the success probability of the cat state generator compared to its implementation in a single PNR detector version and imposes less requirements on ideal PNR detectors. We prove that the fidelity of the output SCSs and its success probability are in conflict with each other (which can be quantified) in a scheme with ineffective PNR detectors, especially when subtracting large (say, 100) number of photons, i.e., increasing the fidelity to perfect values leads to a sharp decrease in the success probability. In general, the strategy of subtracting up to 20 photons from initial SMSV in setup with two BSs is acceptable for achieving sufficiently high values of the fidelity and success probability at the output of the generator of the SCSs of amplitude <3 with two inefficient PNR detectors.