Subgap Kinetic Inductance Detector Sensitive to 85-GHz Radiation

We have fabricated an array of subgap kinetic inductance detectors (SKIDs) made of granular aluminum (T$_{c}$∼2 K) sensitive in the 80–90 GHz frequency band and operating at 300 mK. We measure a noise equivalent power of 1.3×10$^{Zahl}$-16W/Hz$^{Zahl}$0.5 on average and 2.6×10$^{-17}$W/Hz$^{0.5}$ at best, for an illuminating power of 50 fW per pixel. Even though the circuit design of SKIDs is identical to that of the kinetic inductance detectors, the SKIDs operating principle is based on their sensitivity to subgap excitations. This detection scheme is advantageous because it avoids having to lower the operating temperature proportionally to the lowest detectable frequency. The SKIDs presented here are intrinsically selecting the 80–90 GHz frequency band, well below the superconducting spectral gap of the film, at approximately 180 GHz

Circuit Quantum Electrodynamics of Granular Aluminum Resonators

The introduction of crystalline defects or dopants can give rise to so-called "dirty superconductors", characterized by reduced coherence length and quasiparticle mean free path. In particular, granular superconductors such as Granular Aluminum (GrAl), consisting of remarkably uniform grains connected by Josephson contacts have attracted interest since the sixties thanks to their rich phase diagram and practical advantages, like increased critical temperature, critical field, and kinetic inductance. Here we report the measurement and modeling of circuit quantum electrodynamics properties of GrAl microwave resonators in a wide frequency range, up to the spectral superconducting gap. Interestingly, we observe self-Kerr coefficients ranging from $10^{-2}$ Hz to $10^5$ Hz, within an order of magnitude from analytic calculations based on GrAl microstructure. This amenable nonlinearity, combined with the relatively high quality factors in the $10^5$ range, open new avenues for applications in quantum information processing and kinetic inductance detectors.Comment: 7 pages, 4 figures, supplementary informatio

Demonstration of a parity-time symmetry breaking phase transition using superconducting and trapped-ion qutrits

Scalable quantum computers hold the promise to solve hard computational problems, such as prime factorization, combinatorial optimization, simulation of many-body physics, and quantum chemistry. While being key to understanding many real-world phenomena, simulation of non-conservative quantum dynamics presents a challenge for unitary quantum computation. In this work, we focus on simulating non-unitary parity-time symmetric systems, which exhibit a distinctive symmetry-breaking phase transition as well as other unique features that have no counterpart in closed systems. We show that a qutrit, a three-level quantum system, is capable of realizing this non-equilibrium phase transition. By using two physical platforms - an array of trapped ions and a superconducting transmon - and by controlling their three energy levels in a digital manner, we experimentally simulate the parity-time symmetry-breaking phase transition. Our results indicate the potential advantage of multi-level (qudit) processors in simulating physical effects, where additional accessible levels can play the role of a controlled environment.Comment: 14 pages, 9 figure

Образование трет-бутилдифенилметилнитроксильного радикала в реакции дикротоната трифенилвисмута и C-фенил-N-трет-бутилнитрона в бензоле

Decomposition of triphenylbismuth dicrotonate in diffused light in bensene in the presence of spin trap of C-phenyl-N-tert-butylnitrone leads to formation of phenyl radicals which are registered as the adduct PhCH(Ph)N(O•)Bu-t.Triphenylbismuth dicrotonate Ph3Bi(O2CCH=CHCH3)2 in benzene solition in the presence of C-phenyl-N-tert-butylnitrone PhCH=N(O)Bu-t decomposes in light. An adduct of phenyl radical and spin trap PhCH(Ph)N(O•)Bu-t was registered by ESR method.Распад дикротоната трифенилвисмута на рассеянном свету в бензоле в присутствии спиновой ловушки C-фенил-N-трет-бутилнитрона приводит к образованию фенильных радикалов, которые регистрируются как аддукт PhCH(Ph)N(O•)Bu-t.Дикротонат трифенилвисмута Ph3Bi(O2CCH=CHCH3)2 в присутствии C-фенил-N-трет-бутилнитрона PhCH=N(O)Bu-t на свету распадается в бензоле. Аддукт фенильного радикала и спиновой ловушки PhCH(Ph)N(O•)Bu-t был зафиксирован методом ЭПР

Circuit quantum electrodynamics of granular aluminum resonators

Granular aluminum (grAl) is a promising high kinetic inductance material for detectors, amplifiers, and qubits. Here we model the grAl structure, consisting of pure aluminum grains separated by thin aluminum oxide barriers, as a network of Josephson junctions, and we calculate the dispersion relation and nonlinearity (self-Kerr and cross-Kerr coefficients). To experimentally study the electrodynamics of grAl thin films, we measure microwave resonators with open-boundary conditions and test the theoretical predictions in two limits. For low frequencies, we use standard microwave reflection measurements in a low-loss environment. The measured low-frequency modes are in agreement with our dispersion relation model, and we observe self-Kerr coefficients within an order of magnitude from our calculation starting from the grAl microstructure. Using a high-frequency setup, we measure the plasma frequency of the film around 70 GHz, in agreement with the analytical prediction. © 2018, The Author(s