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 explore theoretically the optical response properties in an optomechanical system under electromagneti- cally induced transparency condition but with mechanical resonator being driven by additional coherent field. In this configuration, more complex quantum and interference phenomena occur. partic- ular, we find that probe transmission spectra depend on total phase of applied fields. Our study also provides efficient way to control propagation amplification.

The photonic router is a key device in optical quantum networks. Conventional routers, however, can only transfer photon from the input port to desired probabilistically. Here, we propose use chiral photon-atom interactions for targeted routing that single an arbitrarily selected output deterministically, i.e., with $100%$ probability. configuration of proposed consists driven three-level atom which chirally coupled two waveguides simultaneously. It shown that, by properly adjusting driving...

We propose an experimentally realizable method to control the coupling between two flux qubits. In our proposal, bias fluxes are always fixed for these inductively coupled The detuning of qubits can be initially chosen sufficiently large, so that their initial interbit is almost negligible. When a variable frequency or time-dependent magnetic (TDMF) applied one qubits, well-chosen TDMF used compensate and couple This proposed avoids fast changes either qubit frequencies amplitudes through...

Going beyond the entanglement of microscopic objects (such as photons, spins, and ions), here we propose an efficient approach to produce control quantum three macroscopic coupled superconducting qubits. By conditionally rotating, one by one, selected Josephson-charge qubits, show that their Greenberger-Horne-Zeilinger (GHZ) entangled states can be deterministically generated. The existence GHZ correlations between these qubits could experimentally demonstrated effective single-qubit...

We propose an approach to coherently transfer populations between selected quantum states in one- and two-qubit systems by using controllable Stark-chirped rapid adiabatic passages. These evolution-time insensitive transfers, assisted easily implementable single-qubit phase-shift operations, could serve as elementary logic gates for computing. Specifically, this proposal be conveniently demonstrated with existing Josephson phase qubits. Our can find immediate application the readout of these...

We present the normal-mode splitting and optomechanically induced transparency or absorption phenomena in strongly tunnel-coupled optomechanical cavities. In probe output spectrum, there appear central windows peaks around which two broad sidebands are symmetrically located. It has been confirmed by quantitative findings that sidebands, include distorted peaks, indicate of hybridized cavities, character interference interactions. Additionally, switching from to amplification can be realized...

We demonstrate photon-noise limited performance at sub-millimeter wavelengths in feedhorn-coupled, microwave kinetic inductance detectors made of a TiN/Ti/TiN trilayer superconducting film, tuned to have transition temperature 1.4 K. Micro-machining the silicon-on-insulator wafer backside creates quarter-wavelength backshort optimized for efficient coupling 250 μm. Using frequency read out and when viewing variable blackbody source, we measure device noise consistent with photon incident...

We propose a spectroscopic approach to probe tiny vibrations of nanomechanical resonator (NAMR), which may reveal classical or quantum behavior depending on the decoherence-inducing environment. Our proposal is based detection voltage-fluctuation spectrum in superconducting transmission line (TLR), {\it indirectly} coupled NAMR via controllable Josephson qubit acting as transducer. The (quantum mechanical) induce symmetric (asymmetric) Stark shifts levels, can be measured by voltage...

We propose a mechanism to interface transmission line resonator (TLR) with nanomechanical (NAMR) by commonly coupling them charge qubit, Cooper-pair box controllable gate voltage. Integrated in this quantum transducer or simple network, the qubit plays role of node coherently exchanging information between TLR and NAMR. With such an interface, quasiclassical state NAMR can be created controlling single-mode classical current TLR. Alternatively, ``Cooper pair'' coherent output through driven...

We demonstrate photon counting at 1550 nm wavelength using microwave kinetic inductance detectors (MKIDs) made from TiN/Ti/TiN trilayer films with superconducting transition temperature Tc≈ 1.4 K. The have a lumped-element design large interdigitated capacitor covered by aluminum and inductive absorbers whose volume ranges 0.4 μm3 to 20 μm3. energy resolution improves as the absorber is reduced. achieved an of 0.22 eV resolved up 7 photons per optical pulse, both greatly improved previously...

Quantum routers are the necessary elements of quantum information network, and thus their routing capabilities particularly important. With atomic mirrors robustly controlling reflected or transmitted coefficient waveguide photon, we show that a two-level atom can be served as an ideal router to redirect single photon from input into output waveguides (OWGs) with designable probabilities, e.g., $100%$ for one OWG, $1/2$ two OWGs, $1/3$ three etc.. The influence dissipations on capability is...

Abstract A Josephson radiation threshold detector (JRTD) that is based on the behaviour of a current bias junction (CBJJ) designed and fabricated for infrared (IR@1550nm) detection at low temperatures. To achieve optimal performance, we develop binary hypothesis method to calibrate behaviours (i.e. switching distributions CBJJ with Al/AlO x /Al junction) in absence presence radiation. In IR radiation, transitioned measurable voltage drop across junction, this signal was treated as events H 0...

We study the multi-photon energy resolution and demonstrate photon counting up to about 30 photons at near-infrared wavelengths in a kinetic inductance detector made from aluminum (Al) film. The has lumped-element design comprising large interdigitated capacitor parallel with narrow inductive strip. A fiber-coupled lens is used focus light onto absorber minimize scattering. Detectors different designs film thicknesses are studied. From histogram of optimally filtered response pulse height,...

The measurement of image similarity represents a fundamental task within the domain processing, enabling application sophisticated computational techniques to ascertain degree between two images. To enhance performance these algorithms, academic community has investigated range quantum algorithms. Notably, swap test-based inner product algorithm (ST-QIP) emerged as pivotal method for computing similarity. However, inherent destructive nature test necessitates multiple state evolutions and...

Current-biased Josephson junctions (CBJJs) have been demonstrated as sensitive threshold detectors (JTDs) in the infrared range. In this letter, we show kind of detector could also be used to detect broadband microwave photons. Based on numerical simulations noise-driving phase dynamics an underdamped junction, driven by low-frequency triangular wave current, argue that photons flowing across JJ can detected probing voltage switched signals JJ. Experimentally, designed and fabricated...

Bell inequality violation has been widely tested by using the bipartite entangled pure states and properly encoding local observables in various experimental platforms, detector-, local-, random loopholes have already closed. A natural question is, how to deliver observables? Here, we show that is directly related coherence degree, which controllable different into state. With usual space-like correlation detections, degree can be measured thus nonlocality tested. The feasibility of proposal...

Given that the Hawking radiation from celestial black holes is extremely weak and thus difficult to be practically detected, a series of analogue have been constructed observe relevant radiations in laboratory. Based on critical behavior group velocity microwave signal propagating along controllable composite right/left-handed transmission line, this paper, we theoretically demonstrate an electromagnetic hole (EBH) can co-moving coordinate system, i.e., space, horizon such analogous could...

Superconducting transmission line resonators (TLRs) have been widely applied to circuit quantum electrodynamical systems for superconducting computation and single-photon detections. Recently, such a right-handed TLR has generalized electromagnetic metamaterials (MTMs), its unconventional mode structure experimentally characterized (Wang et al. in Phys Rev Appl 11:054062, 2019). Here, we demonstrate another kind of MTM TLR, i.e., the quarter-wavelength composite right/left-handed (CRLH) TLRs...

We propose how to generate macroscopic quantum superposition states using a microwave cavity containing superconducting charge qubit. Based on the measurement of states, we show that superpositions two macroscopically distinguishable coherent single-mode field can be generated by controllable interaction between and After such are created, switched off classical magnetic field, there is no information transfer also discuss generation squeezed states.

Based on the interaction between radiation field and a superconductor, we propose way to engineer quantum states using SQUID charge qubit inside microcavity. This device can act as deterministic single-photon source well generate any Fock an arbitrary superposition of for cavity field. The controllable be realized by tunable gate voltage classical magnetic applied SQUID.

We propose an approach to reconstruct any superconducting charge qubit state by using quantum tomography. This procedure requires a series of measurements on large enough number identically prepared copies the system. The experimental feasibility this is explained and time scales for different operations are estimated according experimentally accessible parameters. Based tomography, we also investigate possibility process

Exploiting the intrinsic nonlinearity of superconducting Josephson junctions, we propose a scalable circuit with qubits (SCQs) which is very similar to successful one now being used for trapped ions. The SCQs are coupled "vibrational" mode provided by LC or its equivalent (e.g., SQUID). Both single-qubit rotations and qubit-LC-circuit couplings/decouplings can be controlled frequencies time-dependent magnetic fluxes. since qubit-qubit interactions, mediated circuit, selectively performed,...

Abstract Quantum coherence is one of the old but always important concepts in quantum mechanics, and now it has been regarded as a necessary resource for information processing metrology. However, question how to quantify just paid attention recently (see, e.g., Baumgratz et al . PRL, 113. 140401 (2014)). In this paper we verify that well-known Fisher (QFI) can be utilized coherence, satisfies monotonicity under typical incoherent operations convexity mixing states. Differing from most pure...