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arXiv:2209.13491 · AVS Quantum Science

Waveguided sources of consistent, single-temporal-mode squeezed light: The good, the bad, and the ugly

Martin Houde, Nicolás Quesada

Published Feb 27, 2023• 23 citations
arXivHTMLPDF

Abstract

We study theoretically how the brightness of the pumps, with fixed profiles, affects the temporal mode structure of squeezed states generated by fixed parametric waveguided sources. We find that the temporal modes of these squeezed states can be partially mismatched and thus distinguishable, which is undesirable when using these states as resources for quantum computing or heralded state generation. By studying common frequency filtering techniques used experimentally, we find that although one can regain indistinguishability, it comes at the price of potentially greatly reducing the purity of the state. We consider three different source configurations: unapodized single pass, apodized single pass, and apodized double pass. We find that the double pass configuration produces optimal results with almost perfectly indistinguishable states over varying degrees of brightness.

DOI
10.1116/5.0133009

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We study theoretically how the brightness of the pumps, with fixed profiles, affects the temporal mode structure of squeezed states generated by fixed parametric waveguided sources. We find that the temporal modes of these squeezed states can be partially mismatched and thus distinguishable, which is undesirable when using these states as resources for quantum computing or heralded state generation. By studying common frequency filtering techniques used experimentally, we find that although one can regain indistinguishability, it comes at the price of potentially greatly reducing the purity of the state. We consider three different source configurations: unapodized single pass, apodized single pass, and apodized double pass. We find that the double pass configuration produces optimal results with almost perfectly indistinguishable states over varying degrees of brightness.
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Nowadays, the realization of quantum computations and communications based on continuous variables has attracted a significant attention due to a substantial expansion of the system dimensionality. The main progress in this area is attributed to the implementation of multimode systems based on squeezed states of light. One of the simplest ways to generate such states relies upon their producing in a single-pass optical parametric amplifier (OPA) using ultrafast pumping. However, for homodyne detection of such multimode states, the profile of the local oscillator (LO) must perfectly match the profile of the measured mode. Usually, this is not the case; therefore a proper treatment of multimode squeezing is required. In this work, we study both theoretically and experimentally the multimode squeezed light generated in type-0 and type-II OPA. We characterize such sources and investigate the degree of squeezing in dependence on the LO spectral profile, employing a pulse shaping technique. The theoretical analysis is performed using the Schmidt-mode theory. This work might have a significant impact on the realization of multimode quantum protocols
Squeezed light has evolved into a powerful tool for quantum technology, ranging from quantum-enhanced sensing and quantum-state engineering based on partial postselection techniques.The pulsed generation of squeezed light is of particular interest, as it can provide accurate time stamps and a physically defined temporal mode, which are highly preferred in complex communication networks and large-scale information processing.However, the multimode feature of pulsed squeezing limits the purity of the output state, negatively impacting its application in quantum technology.Previous demonstrations and analysis of pulsed squeezing focus on single-pass configurations and synchronously pumped free-space cavities.In this paper, we propose a different approach to generate pulsed squeezing with high temporal purity, where a parametric down-conversion process in integrated photonic cavities is pumped by a single-pass pulse.We show that the effective mode number of the output pulsed squeezing approaches unity.Such a high-purity squeezed light can be realized with broad parameters and a low pump power, providing a robust approach to generating large-scale quantum resources.