arXiv subjects

G. P. Fedorov

Publications and source records attributed to G. P. Fedorov.

5 recordsLinked to original sources

arXiv2022

Overcoming photon blockade in circuit QED single-atom maser with engineered metastability and strong coupling

Reaching high cavity population with a coherent pump in the strong-coupling regime of a single-atom laser is impossible due to the photon blockade effect. In this work, we experimentally demonstrate that in a single-atom maser based on a transmon strongly coupled to two resonators it is possible to pump over a dozen of photons into the system. The first high-quality resonator plays a role of usual lasing cavity, and the second one presents a controlled dissipation channel, bolstering population inversion, and modifies the energy level structure to lift the blockade. As a confirmation of lasing action, we observe conventional laser features such as the narrowing of emission linewidth and external signal amplification. Additionally, we report unique single-atom features: self-quenching and several lasing thresholds.

quant-ph↗

arXiv2020

Single-atom maser with engineered circuit for population inversion

We present a blueprint for a maser with a single three-level transmon superconducting artificial atom. The system can be pumped coherently via a two-photon process, and to achieve high population inversion, the relaxation rate of the metastable state is increased via an auxiliary low-Q cavity coupled to a transition between the transmon excited states. We show numerically that such a maser can operate both in the intermediate coupling regime with super-Poissonian photon statistics and in the strong coupling regime, where the statistics is sub-Poissonian. For the former, the maser exhibits thresholdless behavior and for the latter, there is a well-defined pumping threshold. A useful side-effect of the auxiliary resonator is that it allows to overcome the photon blockade effect for the pump, which would otherwise prevent high photon population. Finally, we observe the bistability of the steady-state Wigner function and the self-quenching effect for some parameters.

quant-ph↗

arXiv2020

Photon transport in a Bose-Hubbard chain of superconducting artificial atoms

We demonstrate non-equilibrium steady-state photon transport through a chain of five coupled artificial atoms simulating the driven-dissipative Bose-Hubbard model. Using transmission spectroscopy, we show that the system retains many-particle coherence despite being coupled strongly to two open spaces. We show that system energy bands may be visualized with high contrast using cross-Kerr interaction. For vanishing disorder, we observe the transition of the system from the linear to the nonlinear regime of photon blockade in excellent agreement with the input-output theory. Finally, we show how controllable disorder introduced to the system suppresses this non-local photon transmission. We argue that proposed architecture may be applied to analog simulation of many-body Floquet dynamics with even larger arrays of artificial atoms paving an alternative way to demonstration of quantum supremacy

quant-ph↗

arXiv2020

Light-dressing of a diatomic superconducting artificial molecule

In this work, we irradiate a superconducting artificial molecule composed of two coupled tunable transmons with microwave light while monitoring its state via joint dispersive readout. Performing high-power spectroscopy, we observe and identify a variety of single- and multiphoton transitions. We also find that at certain fluxes, the measured spectrum of the system deviates significantly from the solution of the stationary Schrödinger equation with no driving. We reproduce these unusual spectral features by solving numerically the full master equation for a steady-state and attribute them to an Autler-Townes-like effect in which a single tone is simultaneously dressing the system and probing the transitions between new eigenstates. We show that it is possible to find analytically the exact frequencies at which the satellite spectral lines appear by solving self-consistent equations in the rotating frame. Our approach agrees well with both the experiment and the numerical simulation.

physics.atom-ph↗

arXiv2019

Automated analysis of single-tone spectroscopic data for cQED systems

Physical systems for quantum computation require calibration of the control parameters based on their physical characteristics by performing a chain of experiments that gather most precise information about the given device. It follows that there is a need for automated data acquisition and interpretation. In this work, we have developed a tool that allows for automatic analysis of single-tone spectroscopy (STS) results for a single cell consisting of qubit and resonator in the circuit quantum electrodynamics (cQED) architecture. Using analytic approaches and maximum likelihood estimation, our algorithm is capable of finding all relevant physical characteristics of the cell by using only the measured STS data. The described approach is fast and robust to noise, and its open-source Python implementation can readily be used to calibrate transmon qubits coupled to notch-port resonators.

quant-ph↗