Hybrid quantum circuits combine two or more physical systems, with the goal of harnessing advantages and strengths different systems in order to better explore new phenomena potentially bring about novel technologies. This article presents a brief overview progress achieved so far field hybrid involving atoms, spins solid-state devices (including superconducting nanomechanical systems). How these elements from atomic physics, optics, condensed matter nanoscience is discussed, possible...

We analyze the optical selection rules of microwave-assisted transitions in a flux qubit superconducting quantum circuit (SQC). show that parities states relevant to phase SQC are well defined when external magnetic ${\ensuremath{\Phi}}_{\mathrm{e}}={\ensuremath{\Phi}}_{0}/2$; then same as ones for electric-dipole usual atoms. When ${\ensuremath{\Phi}}_{\mathrm{e}}\ensuremath{\ne}{\ensuremath{\Phi}}_{0}/2$, symmetry potential artificial ``atom'' is broken, so-called...

We experimentally demonstrate magnon Kerr effect in a cavity-magnon system, where magnons small yttrium iron garnet (YIG) sphere are strongly but dispersively coupled to the photons three-dimensional cavity. When YIG is pumped generate considerable magnons, yields perceptible shift of cavity's central frequency and more appreciable shifts modes. derive an analytical relation between drive power for uniformly magnetized find that it agrees very well with experimental results Kittel mode. Our...

A flux qubit can have a relatively long decoherence time at the degeneracy point, but away from this point is greatly reduced by dephasing. This limits practical applications of qubits. Here we propose design modified commonly used introducing an additional capacitor shunted in parallel to smaller Josephson junction (JJ) loop. Our results show that effects noise be considerably suppressed, particularly both reducing coupling energy JJ and increasing shunt capacitance. capacitance provides...

We report the experimental observation of high-order sideband transitions at single-photon level in a quantum circuit system flux qubit ultrastrongly coupled to coplanar waveguide resonator. With coupling strength reaching 10% resonator's fundamental frequency, we obtain clear signatures higher order red-sideband and first-order blue-sideband transitions, which are mainly due ultrastrong Rabi coupling. Our advances understanding systems paves way study processes model level.

Quantum entanglement in mechanical systems is not only a key signature of macroscopic quantum effects, but has wide applications technologies. Here we proposed an effective approach for creating strong steady-state between two directly coupled oscillators (or oscillator and microwave resonator) modulated optomechanical system. The achieved by combining the processes cavity cooling two-mode parametric interaction, which can surpass bound on maximal stationary from interaction. In principle,...

Cavity magnomechanics has recently become a new platform for studying macroscopic quantum phenomena. The magnetostriction induced vibration mode of large-size ferromagnet or ferrimagnet reaching its ground state represents genuine state. Here we study the ground-state cooling mechanical in cavity magnomechanical system, and focus on role magnon squeezing improving efficiency. is obtained by exploiting self-Kerr nonlinearity. We find that can significantly even completely suppress Stokes...

We study the two-particle quantum Zeno dynamics with a type of nondeterministic collective measurement whose outcome indicates whether state has been collapsed to $\ensuremath{\mid}11⟩$. Such threshold detection, when used continuously, can lead nontrivial dynamics. show that such be produce entanglement almost deterministically. then numerically robustness method and we find operational errors small-angle rotations do not accumulate. also propose possible implementation using...

Using superconducting quantum-circuit elements, we propose an approach to experimentally construct a Kitaev lattice, which is anisotropic spin model on honeycomb lattice with three types of nearest-neighbor interactions and having topologically protected ground states. We study two particular parameter regimes demonstrate both vortex bond-state excitations. Our proposal outlines realizable artificial many-body system that exhibits exotic topological properties.

We propose how to realize high-fidelity quantum storage using a hybrid architecture including two coupled flux qubits and nitrogen-vacancy center ensemble (NVE). One of the is considered as computing processor NVE serves memory. By separating memory units, influence process on can be effectively eliminated, hence an arbitrary state qubit could achieved with high fidelity. Furthermore present proposal robust respect fluctuations system parameters, it experimentally feasibile currently...

We propose an experimentally realizable hybrid quantum circuit for achieving a strong coupling between spin ensemble and transmission-line resonator via superconducting flux qubit used as data bus. The resulting can be to transfer information the resonator. In particular, in contrast direct without bus, our approach requires far less spins achieve (e.g., three four orders of magnitude less). This proposed could enable long-time memory when storing ensemble, allows possibility explore...

A semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC) can be used to achieve a qubit. In contrast spin qubit, the qubit respond an external ac electric field, effect called electric-dipole resonance. Here we develop theory that apply in SOC regime. We find there is optimal strength ${\ensuremath{\eta}}_{\mathrm{opt}}=\sqrt{2}/2$, where Rabi frequency induced by field becomes maximal. Also, show both level spacing and of have periodic responses direction static magnetic...

We present an experimentally implementable method to couple Josephson charge qubits and generate detect macroscopic entangled states. A large-junction superconducting quantum interference device is used in the qubit circuit for both coupling implementing readout. Also, we explicitly show how achieve a microwave-assisted entanglement coupled-qubit system.

We propose a tunable on-chip micromaser using superconducting quantum circuit (SQC). By taking advantage of externally controllable state transitions, population inversion can be achieved and preserved for the two working levels SQC and, when needed, generate single photon. regularly repeat these processes in each cycle previously generated photon cavity is decaying, so that periodic sequence photons produced persistently. This provides way implementing persistent single-photon source on...

We propose an approach for cooling both artificial atom (e.g., a flux qubit) and its neighboring quantum system, the latter modeled by either two-level system or resonator. The qubit is cooled manipulating states, following inverse process of state population inversion, then switched on to resonantly interact with system. By repeating these steps, two subsystems can be simultaneously cooled. Our results show that this robust effective, irrespective chosen systems connected qubit.

We use a non-Markovian approach to study the decoherence dynamics of qubit in either low- or high-frequency bath modeling environment. This is done for two separate cases: with measurements without them. based on unitary transformation and does not require rotating-wave approximation. In case measurement, we show that, low-frequency noise, shifts energy toward higher energies (blue shift), while ordinary cutoff Ohmic lower (red shift). order preserve coherence qubit, also investigate subject...

We investigate the spontaneous emission (SE) spectrum of a qubit in lossy resonant cavity. use neither rotating-wave approximation nor Markov approximation. For weak-coupling case, SE is single peak, with its location depending on spectral density environment. Then, asymmetry (of and heights two peaks) peaks (which are related to vacuum Rabi splitting) changes as qubit–cavity coupling increases. Explicitly, for low-frequency intrinsic bath, height splitting enhanced strength However, an...

Electromagnetically induced transparency (EIT) has been realized in atomic systems, but fulfilling the EIT conditions for artificial atoms made from superconducting circuits is a more difficult task. Here we report an experimental observation of tunable three-dimensional transmon by probing cavity transmission. To fulfill conditions, tune to adjust its damping rates utilizing effect on states. From observations, clearly identify and Autler-Townes splitting (ATS) regimes as well transition...

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Senescence-associated secretory phenotype (SASP) mediates the biological effects of senescent cells on tissue microenvironment and contributes to ageing-associated disease progression. ACSS2 produces acetyl-CoA from acetate epigenetically controls gene expression through histone acetylation under various circumstances. However, whether how regulates cellular senescence remains unclear. Here, we show that pharmacological inhibition deletion Acss2 in mice blunts SASP abrogates pro-tumorigenic...

Highly entangled states called cluster are a universal resource for measurement-based quantum computing (QC). Here we propose an efficient method producing large using superconducting circuits. We show that state can be efficiently generated in just one step by turning on the interqubit coupling short time. Because is only switched during time interval generating state, our approach also convenient preparing initial each qubit and implementing one-way QC via single-qubit measurements....

Majorana fermions are long-sought exotic particles that their own antiparticles. Here we propose to utilize superconducting circuits construct two superconducting-qubit arrays where modes can occur. A so-called qubit is encoded by using the unpaired modes, which emerge at left and right ends of chain in Majorana-fermion representation. We also show this spin representation its advantage, over a single qubit, regarding quantum coherence. Moreover, use four qubits as smallest system...

A wide class of exact master equations for a multiple qubit system can be explicitly constructed by using the corresponding non-Markovian quantum-state diffusion equations. These arise naturally from quantum decoherence dynamics as memory coupled to collective colored noisy source. The are also important in optimal control, dissipation, and thermodynamics. In this paper, we show that equation dissipative $N$-qubit derived statistical average trajectories. We illustrated our general...