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AIP conference proceedings

Measurement system of correlation functions of microwave single photon source in real time

A. Korenkov, A. Yu. Dmitriev, O. V. Astafiev

Published Jan 1, 2018• 0 citations

Abstract

Several quantum setups, such as quantum key distribution networks[1] and quantum simulators (e.g. boson sampling), by their design rely on single photon sources (SPSs). These quantum setups were demonstrated to operate in optical frequency domain. However, following the steady advances in circuit quantum electrodynamics, a proposal has been made recently[2] to demonstrate boson sampling with microwave photons. This in turn requires the development of reliable microwave SPS. It’s one of the most important characteristics are the first-order and the second-order correlation functions g1 and g2. The measurement technique of g1 and g2 is significantly different from that in the optical domain [3],[4] because of the current unavailability of microwave single-photon detectors. In particular, due to high levels of noise present in the system a substantial amount of statistics in needed to be acquired. This work presents a platform for measurement of g1 and g2 that processes the incoming data in real time, maximizing the efficiency of data acquisition. The use of field-programmable gate array (FPGA) electronics, common in similar experiments[3] but complex in programming, is avoided; instead, the calculations are performed on a standard desktop computer. The platform is used to perform the measurements of the first-order and the second-order correlation functions of the microwave SPS.

DOI: 10.1063/1.5025446

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Abstract This paper presents a correlator for constructing the second-order autocorrelation function g(2)(τ), implemented on a field-programmable gate array (FPGA). The device is designed for high-precision recording of time intervals between photons detected from single emitters. The use of an FPGA makes it possible to achieve a time resolution of 185 ps and real-time event processing. Experimental data confirming the achievement of photon antibunching with g(2)(0) < 0.5, characteristic of single quantum emitters, are demonstrated. The device can be used to analyze photon correlations in quantum optics problems and when working with single quantum emitters.

A correlator for constructing the second-order autocorrelation function g(2)(τ) implemented on a field-programmable gate array (FPGA) is presented. The device is intended for high-precision recording of time intervals between photons emitted by single emitters. Using an FPGA made it possible to achieve a temporal resolution of 185 ps and real-time event processing. Experimental data confirming the achievement of photon antibunching with g(2)(0) < 0.5, which is typical for single quantum emitters, are demonstrated. The device can be used for analyzing photon correlations in tasks of quantum optics and when working with single quantum emitters.

Superconducting circuits have been successfully established as systems to prepare and investigate microwave light fields at the quantum level. In contrast to optical experiments where light is detected using photon counters, microwaves are usually measured with well developed linear amplifiers. This makes measurements of correlation functions - one of the important tools in optics - harder to achieve because they traditionally rely on photon counters and beam splitters. Here, we demonstrate a system where we can prepare on demand single microwave photons in a cavity and detect them at the two outputs of the cavity using linear amplifiers. Together with efficient data processing, this allows us to measure different observables of the cavity photons, including the first-order correlation function. Using these techniques we demonstrate cooling of a thermal background field in the cavity.

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Single-photon sources are crucial for quantum information technologies. Here, we demonstrate a microwave single-photon source fabricated using a tantalum-based thin film, whose favorable material properties enable high-quality and stable photon emission. The antibunching behavior of the emitted radiation is revealed by second-order correlation measurements. Furthermore, traveling-wave parametric amplifiers are used as the pre-amplifier in the detection chains, we substantially improve the signal-to-noise ratio and thereby greatly reduce the acquisition time required for second-order correlation measurements. These results demonstrate the viability of tantalum-based superconducting devices as reliable platforms for microwave quantum photonics.