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arXiv:2107.08113 · Physical Review Applied

Single-Photon Detection with a Josephson Junction Coupled to a Resonator

Dmitry S. Golubev, Evgeni V. Il’ichev, L. S. Kuzmin

Published Jul 9, 2021• 22 citations
arXivHTMLPDF

Abstract

We use a semiclassical formalism to optimize a microwave single-photon detector based on switching events of a current-biased Josephson junction coupled to a resonator. To detect very rare events, the average time between dark counts ${\ensuremath{\tau}}_{\mathrm{dark}}$ should be maximized taking into account that the switching time ${\ensuremath{\tau}}_{\mathrm{sw}}$ should be sufficiently small. We demonstrate that these times can be tuned in a wide range by changing the junction parameters, and ${\ensuremath{\tau}}_{\mathrm{dark}}/{\ensuremath{\tau}}_{\mathrm{sw}}\ensuremath{\sim}{10}^{9}$ can be achieved. Therefore, a junction-resonator arrangement can be used to detect extremely low photon fluxes (e.g., for searching for galactic axions).

DOI
10.1103/physrevapplied.16.014025

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We use a semiclassical formalism to optimize a microwave single-photon detector based on switching events of a current-biased Josephson junction coupled to a resonator. To detect very rare events, the average time between dark counts \ensuremathτdark{\ensuremath{\tau}}_{\mathrm{dark}}\ensuremathτdark​ should be maximized taking into account that the switching time \ensuremathτsw{\ensuremath{\tau}}_{\mathrm{sw}}\ensuremathτsw​ should be sufficiently small. We demonstrate that these times can be tuned in a wide range by changing the junction parameters, and \ensuremathτdark/\ensuremathτsw\ensuremath∼109{\ensuremath{\tau}}_{\mathrm{dark}}/{\ensuremath{\tau}}_{\mathrm{sw}}\ensuremath{\sim}{10}^{9}\ensuremathτdark​/\ensuremathτsw​\ensuremath∼109 can be achieved. Therefore, a junction-resonator arrangement can be used to detect extremely low photon fluxes (e.g., for searching for galactic axions).
Axions detection requires the ultimate sensitivity down to the single-photon limit. In the microwave region, this corresponds to energies in the yJ range. This extreme sensitivity has to be combined with an extremely low dark-count rate since the probability of axions conversion into microwave photons is supposed to be very low. To face this complicated task, we followed two promising approaches that both rely on the use of superconducting devices based on the Josephson effect. The first one is to use a single Josephson junction (JJ) as a switching detector (i.e., exploiting the superconducting to normal state transition in the presence of microwave photons). We designed a device composed of a coplanar waveguide terminated on a current-biased JJ. We tested its efficiency to pulsed (pulse duration 10 ns) microwave signals since this configuration is closer to an actual axions search experiment. We show how our device is able to reach detection capability of the order of ten photons with the frequency of 8 GHz. The second approach is based on an intrinsically quantum device formed by two resonators coupled only via a superconducting qubit network. This approach relies on quantum nondemolition measurements of the resonator photons. We show that by injecting radiofrequency power into the resonator, the frequency position of the resonant drop in the transmission coefficient (S21) can be modulated up to 4 MHz. We anticipate that, once optimized, both the devices have the potential to reach single-photon sensitivity.
Abstract The major task of detecting axions or axion-like particles has two challenges. On the one hand, the ultimate sensitivity is required, down to the energy of a single microwave photon of the yoctojoule range. On the other hand, since the detected events are supposed to be rare, the dark count rate of the detector must be extremely low. We show that this trade-off can be approached due to the peculiar switching dynamics of an underdamped Josephson junction in the phase diffusion regime. The detection of a few photons’ energy at 10 GHz with dark count time above 10 s and the efficiency close to unity was demonstrated. Further enhancements require a detailed investigation of the junction switching dynamics.
We analyze the quantum efficiency of a microwave photon detector based on a current-biased Josephson junction. We consider the Jaynes-Cummings Hamiltonian to describe coupling between the photon field and the junction. We then take into account the coupling of the junction and the resonator to the environment. We solve the equation of motion of the density matrix of the resonator-junction system to compute the quantum efficiency of the detector as a function of detection time, bias current, and energy relaxation time. Our results indicate that junctions with modest coherence properties can provide efficient detection of single microwave photons, with quantum efficiency in excess of 8080%80.
Abstract Josephson junctions, in appropriate configurations, can be excellent candidates for detection of single photons in the microwave frequency band. Such possibility has been recently addressed in the framework of galactic axion detection. Here are reported recent developments in the modelling and simulation of dynamic behaviour of a Josephson junction single microwave photon detector. For a Josephson junction to be enough sensitive, small critical currents and operating temperatures of the order of ten of mK are necessary. Thermal and quantum tunnelling out of the zero-voltage state can also mask the detection process. Axion detection would require dark count rates in the order of 0.001 Hz. It is, therefore, is of paramount importance to identify proper device fabrication parameters and junction operation point.
We present a novel scheme to detect itinerant microwave radiation at the single photon level. Using existing Josephson-photonics devices, where two microwave cavities are coupled by a dc-voltage biased superconducting junction, we theoretically show how to implement a stroboscopically repeated, near-projective measurement of a photon impinging on one of the cavities. Optimizing rate, duration, and strength of the measurement by flux control of the junction and developing a threshold protocol to detect the photon from a homodyne measurement of the radiation output of the other cavity, we achieve highly efficient detection with low dark counts. By cascading the detector with a preamplifier, where a similar two-cavity Josephson-photonics device acts as a photon multiplier, we can further improve the device to reach a detection efficiency of 88.5%88.5 \%88.5% with a dark count rate of ∼10−4γa\sim10^{-4} γ_a∼10−4γa​, set by the resonance width γaγ_aγa​ of the absorbing cavity. These results for a multiplication factor of two suggest that near-unity efficiencies may be reached for higher multiplication factors.
A growing interest in the detection of single microwave-photons has been stimulated by the search for light dark matter, such as Axions and Axion-like particles, together with the fast development of quantum technologies based on superconducting devices. Many solutions have been proposed in literature but most of them still fail to satisfy the tight requirements imposed by Dark Matter experiments. For instance, many have a large dark-count rate that still make parametric amplifiers a preferable choice. On the contrary, a device based on a current biased Josephson junction resonantly activated by the absorption of a microwave photon may have dark-counts rate down to the mHz level. Here, we report the experimental study of the resonant activation of an Al Josephson junction excited by continuous radiofrequency. The device under study consists of a chip with a transmission line terminated by an Al Josephson-junction, fabricated by shadow-mask evaporation technique. The sample-holder with the chip inside is hosted in a superconducting box and it is thermally anchored to the mixing-chamber plate of a dilution refrigerator at a temperature of about 15 mK. We measured the escape rates of the junction in different configurations of current bias and radiofrequency excitations. Response to continuous wave has been measured and interpreted within the RCSJ model. These results are used to optimize the design of a single microwave-photon detector.