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arXiv:2302.13762

The quantum and classical field scattered on a single two-level system

Sergei Gunin, Andrei Vladimirovich Vasenin, A. Yu. Dmitriev, Konstantin S. Tikhonov, Gleb Fedorov, O. V. Astafiev

Published Feb 27, 2023• 0 citations
arXivHTMLPDF

Abstract

In many problems, the scattering amplitudes of weak coherent pulse are almost equivalent to the ones of single propagating photon. We thoroughly compare the scattering of: (i) short microwave coherent pulse from rf generator and (ii) vacuum-photon coherent superposition from the two-level Emitter, both directed to a single two-level system (the Probe). To do that, we use two superconducting qubits to implement Emitter and Probe, both strongly coupled to the same waveguide. However, with the use of magnetic circulator we couple the field from Emitter to the Probe without reverse backaction, thereby working with a cascaded atomic system implemented in waveguide-QED setup. By measuring the dynamics of scattered field, we find a certain discrepancy between two cases, confirmed by analytical and numerical study. Particularly, we find the optimal amplitude $Ω_{*}$ of classical pulse mimicking the superposition from Emitter, for which the difference becomes very small (but non-vanishing), and is almost unavailable to measure in practice.

DOI
10.48550/arxiv.2302.13762

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In many problems, the scattering amplitudes of weak coherent pulse are almost equivalent to the ones of single propagating photon. We thoroughly compare the scattering of: (i) short microwave coherent pulse from rf generator and (ii) vacuum-photon coherent superposition from the two-level Emitter, both directed to a single two-level system (the Probe). To do that, we use two superconducting qubits to implement Emitter and Probe, both strongly coupled to the same waveguide. However, with the use of magnetic circulator we couple the field from Emitter to the Probe without reverse backaction, thereby working with a cascaded atomic system implemented in waveguide-QED setup. By measuring the dynamics of scattered field, we find a certain discrepancy between two cases, confirmed by analytical and numerical study. Particularly, we find the optimal amplitude Ω∗Ω_{*}Ω∗​ of classical pulse mimicking the superposition from Emitter, for which the difference becomes very small (but non-vanishing), and is almost unavailable to measure in practice.
In many problems, the scattering amplitudes of a weak coherent pulse are almost equivalent to the ones of a single propagating photon. We thoroughly compare the scattering of (i) a short microwave coherent pulse from a rf generator and (ii) a vacuum-photon coherent superposition from the two-level emitter, both directed to a single two-level system---the probe. To do that, we use two superconducting qubits to implement emitter and probe, both strongly coupled to the same waveguide. However, with the use of a magnetic circulator we couple the field from the emitter to the probe without reverse backaction, thereby working with a cascaded atomic system implemented in a waveguide-QED setup. By measuring the dynamics of the scattered field, we find a certain discrepancy between two cases, confirmed by analytical and numerical study. Particularly, we find the optimal amplitude ${\mathrm{\ensuremath{\Omega}}}_{*}$ of classical pulse mimicking the superposition from the emitter, for which the difference becomes very small (but nonvanishing) and is almost unavailable to measure in practice.
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An electromagnetic wave propagating through a waveguide with a strongly coupled two-level superconducting artificial atom exhibits an evolving superposition with the atom. The Rabi oscillations in the atom result from a single excitation-relaxation, corresponding to photon absorption and stimulated emission from and to the field. In this study, we experimentally investigated the time-dependent behavior of the field transmitted through a waveguide with a strongly coupled transmon. The scattered fields agree well with the predictions of the input-output theory. We demonstrate that the time evolution of the propagating fields, because of the interaction, encapsulates all information about the atom. Furthermore, we deduced the dynamics of the incoherent radiation component from the first-order correlation function of the measured field.
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