On the possibility of faster detection of magnetic flux changes in a single-photon counter by RF SQUID with MoRe–Si(W)–MoRe junction

Abstract

The nonhysteretic mode of a RF SQUID with a MoRe–Si(W)–MoRe Josephson junction is analyzed in order to detect the states of a single-photon counter based on a superconducting quantum interferometer with a discrete Hamiltonian. The absorption of a photon with 10 GHz frequency brings the counter to the excited level causing tunnelling into the adjacent potential well and a change in the magnetic flux in the interferometer, which can be detected by the SQUID magnetometer. Measurement of a quantum system requires minimization of the back action of the signal read-out channel at the counter, high sensitivity, and speed of the magnetometer. The MoRe–Si(W)–MoRe contacts are optimized for various concentrations of tungsten (W) in silicon (Si) and barrier layer thickness. It is shown that using MoRe–Si(W)–MoRe contacts with a tungsten concentration of approximately 11% for the RF SQUID at excitation frequencies of ∼1 GHz makes it practically an ideal parametric upward frequency shifter with noise determined by the cooled amplifier.

An RF SQUID readout for a flux qubit-based microwave single photon counter

“…The excitation frequency Ω P /2π ≈ 500 MHz was chosen so that it is much less than the resonant frequency of the qubit (E 1 − E 0 )/ℏ, and does not coincide with the multiphoton absorption peaks of the qubit as a two-level artificial atom. The shunt resistance of the Josephson SIS junction R ≈ 10 Ohm is given by the existing technology [23]. With such a shunt resistance, the parameter that determines nonadiabatic phenomena and losses in the interferometer is quite small, q = Ω P • L/R ≈ 0.06.…”

“…With such a shunt resistance, the parameter that determines nonadiabatic phenomena and losses in the interferometer is quite small, q = Ω P • L/R ≈ 0.06. This value can be reduced by an order of magnitude by using other types of Josephson junctions [20,23,24].…”

Influence of External Magnetic Field on Transport Characteristics of Superconducting Junctions MoRe–Si(W)–MoRe

“…Для формування необхідної геометрії, плівки MoRe і Si(W) осаджували через металеві молібденові маски. Формування W нанокластерів розміром біля 15×50×50 нм 3 всередині шару кремнію товщиною біля 15 нм підтверджено результатами досліджень модельного шару Si(W) більшої товщини за допомогою електронного просвічувального мікроскопа [11], а також результатами експериментальних досліджень шару Si(W) за допомогою атомно-силового мікроскопа [12] Рис. 1.…”