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International Scientific-Technical Conference on Actual Problems of Electronic Instrument Engineering (APEIE)

Detection Efficiency of Microwave Photons by the System of Two Qubits with Relaxation to a Common Bath

O. A. Chuikin, Yakov S. Greenberg

Published Oct 1, 2018• 0 citations
Publisher

Abstract

In this work we calculate the amplitudes of nonradiative decay of the microwave photons for the system of two qubits in a waveguide with energy relaxation to a common bath. The calculations are carried out in the formalism of the effective non-Hermitian Hamiltonian which includes in addition to the local relaxation channels the global relaxation of qubits to a common channel. We showed that for identical qubits the global relaxation can be matched to zero for the certain distances between the qubits. We analyze the contribution of nonradiative decay channels to the detection efficiency of microwave photons by the two-qubit system. We also find the parameters of the system at which the efficiency takes on 100% value.

DOI
10.1109/apeie.2018.8545472

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The influence of nonradiative damping of qubits on the microwave transport of photons propagating in a onedimensional microstrip line has been considered. Expressions for the transmission and reflection coefficients for two qubits have been obtained within the non-Hermitian Hamiltonian formalism. The indirect interaction between qubits caused by nonradiative decay into a common channel is explicitly taken into account in these expressions. It has been shown that this interaction leads to results significantly different from known results.
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In this work, using the non-Hermitian Hamiltonian method, the transmission of a single photon in a one-dimensional waveguide interacting with the cavity containing an arbitrary number of photons and the two-level artificial atom is studied with allowance for the relaxation of the latter. For transport factors, analytical expressions which explicitly take into account the qubit relaxation parameter have been obtained. The form of the transmission (reflection) coefficient when there is more than one photon in the cavity qualitatively differs from the single-photon cavity and contains the manifestation of the photon blockade effect. The qubit lifetime depends on the number of photons in the cavity.
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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.