There is a wide recognition that Josephson-junction-like structures intrinsic to the layered cuprate high temperature superconductors offer an attractive stage for exploiting possible applications new quantum technologies. On other hand low energy quasiparticle excitations characteristically present in these d-wave may easily destruct coherence required. Here we demonstrate first time feasibility of macroscopic tunneling Josephson junctions superconductor, and find it be characterized by...

Kerr cat qubits are a promising candidate for fault-tolerant quantum computers owing to the biased nature of their errors. The $ZZ$ coupling between can be utilized two-qubit entangling gate, but residual called crosstalk is detrimental precise computing. In order resolve this problem, we propose tunable $ZZ$-coupling scheme using two transmon couplers. By setting detunings couplers at opposite values, couplings via cancel each other out. We also apply our...

We propose a prime factorizer operated in framework of quantum annealing (QA). The idea is inverse operation multiplier implemented with QA-based Boolean logic circuits. designed the QA machine on an application-specific-annealing-computing architecture which efficiently increases available hardware budgets at cost restricted functionality. invertible gates consisting superconducting flux qubits was confirmed by circuit simulation classical noise sources. circuits were and fabricated using...

A Kerr nonlinear parametric oscillator (KPO) can stabilize a quantum superposition of two coherent states with opposite phases, which be used as qubit. In universal gate set for computation KPOs, an $R_x$ gate, interchanges the states, is relatively hard to perform owing stability states. We propose method high-fidelity by exciting KPO outside qubit space parity-selective transitions, implemented only adding driving field. this method, utilization higher effective excited leads faster rather...

We examine the macroscopic quantum tunneling (MQT) in high-${T}_{c}$ superconductor Josephson junctions with a $d$-wave order parameter. Using microscopic Hamiltonian and functional integral method, we analytically obtain MQT rate (the inverse lifetime of metastable state) for $c$-axis twist junctions. In case zero angle, system shows super-Ohmic dissipation due to presence nodal quasiparticle tunneling. Therefore, is strongly suppressed comparison finite angle cases.

We predict anomalous atomic-scale 0-pi transitions in a Josephson junction with ferromagnetic-insulator (FI) barrier. The ground state of such alternates between 0 and pi states when thickness FI is increasing by single atomic layer. find that the mechanism transition can be attributed to thickness-dependent phase shifts wave numbers electrons holes FI. Based on these results, we show stable realized junctions based high-T{c} superconductors La2BaCuO5

Efficient electron-refrigeration based on a normal-metal/spin-filter/superconductor junction is proposed and demonstrated theoretically. The spin-filtering effect leads to values of the cooling power much higher than in conventional normal-metal/nonmagnetic-insulator/superconductor coolers allows for an efficient extraction heat from normal metal. We demonstrate that highly can be realized both ballistic diffusive multi-channel junctions which reduction electron temperature 300 mK around 50...

A practical method for realizing intense terahertz (THz) emission from intrinsic Josephson junctions (IJJs) by utilizing external local-heating is proposed and demonstrated theoretically. An artificial temperature distribution induced local heating strongly excites plasma waves inside IJJs. Accordingly, the power of THz wave enhanced drastically, it can reach order mW. Our result indicates that use heat control a powerful to realize solid-state THz-emitters based on

We theoretically investigate surface plasmon polaritons propagating in the thin-film Weyl semimetals. show how properties of are affected by hybridization between plasmons localized at two metal-dielectric interfaces. Generally, this results new mixed modes, which called short-range and long-range plasmons, respectively. calculate dispersion curves these modes for three principle configurations axion vector describing axial anomaly that partial lack non-reciprocity can be controlled...

Kerr parametric oscillators (KPOs), which can be implemented with superconducting parametrons possessing large nonlinearity, have been attracting much attention in terms of their applications to quantum annealing, universal computation, and studies many-body systems. It is practical importance for these realize fast accurate tunable coupling between KPOs a simple manner. We develop scheme high tunability speed amplitude using the transitionless rotation KPO phase space based on shortcuts...

We theoretically investigate the macroscopic quantum dynamics of a $\ensuremath{\pi}$ junction with superconductor (S) and multiferroic material or ferromagnetic insulator (FI). By deriving effective action from microscopic Hamiltonian, $\ensuremath{\pi}$-junction qubit (a S-FI-S superconducting interference device ring) is proposed. In this qubit, two-level system spontaneously generated effect quasiparticle dissipation found to be very weak. These features make it possible realize quiet...

The switching dynamics of current-biased Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$ intrinsic Josephson junctions (IJJs) was studied to clarify the effect d-wave superconductivity and stack structure on properties. High quality IJJs were fabricated, then temperature dependence probability distribution measured for first second switchings. Although standard deviation detected both switchings showed similar saturation characteristics with decreasing temperature, at about 13 times higher than...

A Boltzmann machine is a powerful tool for modeling probability distributions that govern the training data. thermal equilibrium state typically used learning to obtain suitable distribution. The consists of calculating gradient loss function given in terms average, which most time-consuming procedure. Here, we propose method implement by using noisy intermediate-scale quantum devices. We prepare an initial pure contains all possible computational basis states with same amplitude, and apply...

A theoretical proposal for testing Bell's inequality in mesoscopic systems is presented. We show that the entanglement of two electron spins can be detected spin filter effect semiconductor / ferromagnetic junction. The current-current correlation function calculated by use quantum scattering theory and we compare it with local hidden variable theory. also discuss influence an imperfect derive condition to see violation experimentally.

The macroscopic quantum tunneling (MQT) in the current biased high-Tc superconductor Josephson junctions and effect of zero energy bound states (ZES) on MQT are theoretically investigated. We obtained analytical formula rate showed that presence ZES at normal/superconductor interface leads to a strong Ohmic quasiparticle dissipation. Therefore, is noticeably inhibited compared with c-axis which completely absent.

Abstract In quantum chemistry, it is important to estimate an energy gap between a ground state and excited of molecular Hamiltonians. previous researches, was necessary measure the that separately, estimated from subtraction them. Here, we show novel scheme such in more direct manner. We use concept Ramsey type measurement annealing (QA) for estimation gap. our scheme, measured signal oscillates with frequency To study performance perform numerical simulations. The results robust against...

Abstract Kerr parametric oscillators (KPOs) have attracted increasing attention in terms of their application to quantum information processing and simulations. The state preparation measurement KPOs are typical requirements when used as qubits. methods previously proposed for preparations utilize modulation external fields such a pump drive fields. We study the stochastic stable coherent states KPO with homodyne detection, which does not require fields, thus can reduce experimental efforts...

We study macroscopic quantum tunneling (MQT) in $c$-axis twist Josephson junctions made of high-${T}_{c}$ superconductors order to clarify the influence anisotropic parameter symmetry (OPS) on MQT. The dependence MQT rate angle $\ensuremath{\gamma}$ about $c$ axis is calculated by using functional integral and bounce method. Due $d$-wave OPS, standard deviation switching current distribution crossover temperature from thermal activation are found be given...

We present a quantitative study of the current-voltage characteristics (CVC) diffusive superconductor/ insulator/ ferromagnet/ superconductor (SIFS) tunnel Josephson junctions. In order to obtain CVC we calculate density states (DOS) in F/S bilayer for arbitrary length ferromagnetic layer, using quasiclassical theory. For layer thickness larger than characteristic penetration depth superconducting condensate into F find an analytical expression which agrees with DOS obtained from...

Quantum annealing (QA) is one of the methods to prepare a ground state problem Hamiltonian. In absence noise, QA can accurately estimate ground-state energy if adiabatic condition satisfied. However, in practice, systems are known suffer from decoherence. Meanwhile, considerable research effort has been devoted noisy intermediate-scale quantum (NISQ) computation. For practical NISQ computation, many error-mitigation (EM) have proposed mitigate effects noise. This paper proposes strategy...

We have investigated the proximity effect in superconductor/ferromagnet junctions a systematic manner to discuss relationship between zero-energy peak (ZEP) of local density states (LDOS) and spin-triplet odd-frequency pairing. By exactly solving nonlinear Usadel equations, we found that ZEP is realized wide range geometrical material parameters case noncollinear magnetization. This strongly suggests robustness induced by pairing such systems. also crossover from singlet triplet can be...

We theoretically investigate the decay constant of surface plasmon polaritons in a Weyl semimetal and propose an experimental method for detecting semimetals. It is revealed that polariton exhibits various characteristics depending on wave vector. can be pure wave, pseudosurface couples with bulk plasmon, or generalized complex constants. Such diverse are peculiar to semimetals obey axion electrodynamics. The results suggest measurement length, inverse constant, powerful probe identifying

Electromagnetic pulse propagation in a quantum metamaterial, an artificial, globally coherent optical medium, is numerically simulated. We show that one-dimensional metamaterial based on superconducting bits, initialized easily reachable factorized excited state, demonstrates lasing the microwave range, accompanied by chaotization of qubit states and generation higher harmonics. These effects may provide tool for characterization optimization prototypes.

Quantum annealing (QA) provides us with a way to solve combinatorial optimization problems. In the previous demonstration of QA, superconducting flux qubit (FQ) was used. However, FQs in these demonstrations have short coherence time such as tens nano seconds. For purpose utilize quantum properties, it is necessary use another better time. Here, we propose capacitive-shunted (CSFQ) for implementation QA. The CSFQ has few order magnitude than FQ used We theoretically show that, although...