arXiv subjects

C. P. Sun

Publications and source records attributed to C. P. Sun.

At least 145 records · Page 8Linked to original sources

arXiv2010

Supersymmetric Response of Bose-Fermi Mixture to Photoassociation

We study supersymmetric (SUSY) responses to a photoassociation process in a mixture of Bose molecules $b$ and Fermi atoms $f$ which turn to mutual superpartners for a set of proper parameters. We consider the molecule $b$ to be a bound state of the atom $f$ and another Fermi atom $F$ with different species. The $b$-$f$ mixture and a free $F$ atom gas are loaded in an optical lattice. The SUSY nature of the mixture can be signaled in the response to a photon induced atom-molecule transition: While two new types of fermionic excitations, an individual $b$ particle-$f$ hole pair continuum and the Goldstino-like collective mode, are concomitant for a generic $b$-$f$ mixture, the former is completely suppressed in the SUSY $b$-$f$ mixture and the zero-momentum mode of the latter approaches to an exact eigenstate. This SUSY response can be detected by means of the spectroscopy method, e.g., the photoassociation spectrum which displays the molecular formation rate of $% Ff\to b$.

cond-mat.other↗

arXiv2010

Quantum Zeno switch for single-photon coherent transport

Using a dynamical quantum Zeno effect, we propose a general approach to control the coupling between a two-level system (TLS) and its surroundings, by modulating the energy level spacing of the TLS with a high frequency signal. We show that the TLS--surroundings interaction can be turned on or off when the ratio between the amplitude and the frequency of the modulating field is adjusted to be a zero of a Bessel function. The quantum Zeno effect of the TLS can also be observed by the vanishing of the photon reflection at these zeros. Based on these results, we propose a quantum switch to control the transport of a single photon in a 1D waveguide. Our analytical results agree well with numerical results using Floquet theory.

quant-ph↗

arXiv2009

Asymmetric coherent transmission for single particle diode and gyroscope

We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous to a perfect semiconductor diode where current flows only in one direction. The general result is also valid for a neutral particle system since the effective magnetic flux may be implemented by a globe rotation. This observation means that the three-site system can serve as an orientation measuring gyroscope due to the approximate linear dependence of the current difference of two output leads on the rotational angular velocity.

quant-ph↗

arXiv2009

Topological Peierls Transitions in Möbius Molecular Devices

We study the topological properties of Peierls transitions in a monovalent Möbius ladder. Along the transverse and longitudinal directions of the ladder, there exist plenty Peierls phases corresponding to various dimerization patterns. Resulted from a special modulation, namely, staggered modulation along the longitudinal direction, the ladder system in the insulator phase behaves as a ``topological insulator'', which possesses charged solitons as the gapless edge states existing in the gap. Such solitary states promise the dispersionless propagation along the longitudinal direction of the ladder system. Intrinsically, these non-trivial edges states originates from the Peierls phases boundary, which arises from the non-trivial $\mathbb{Z}^{2}$ topological configuration.

cond-mat.mes-hall↗

arXiv2009

Effective Hamiltonian approach to the Kerr nonlinearity in an optomechanical system

Using the Born-Oppenheimer approximation, we derive an effective Hamiltonian for an optomechanical system that leads to a nonlinear Kerr effect in the system's vacuum. The oscillating mirror at one edge of the optomechanical system induces a squeezing effect in the intensity spectrum of the cavity field. A near-resonant laser field is applied at the other edge to drive the cavity field, in order to enhance the Kerr effect. We also propose a quantum-nondemolition-measurement setup to monitor a system with two cavities separated by a common oscillating mirror, based on our effective Hamiltonian approach.

quant-ph↗

arXiv2009

Spontaneous symmetry breaking in thermalization and anti-thermalization

The phenomenon of spontaneous symmetry breaking is investigated in the dynamic thermalization of a degenerate quantum system. A three-level system interacting with a heat bath is carefully studied to this end. It is shown that the three-level system with degenerate ground states might have different behaviors depending on the details of the interaction with the heat bath when the temperature approaches zero. If we introduce an external field to break the degeneracy of the ground states and let it approach zero after letting the temperature approach zero, then two possibilities will arise: the steady state is a definite one of the degenerate states independent of the initial state, or the steady state is dependent on the initial state in a complicated way. The first possibility corresponds to a spontaneous symmetry breaking of the system and the second one implies that the heat bath could not totally erase the initial information in certain cases.

quant-ph↗

arXiv2009

Thermodynamic witness of quantum probing

The thermodynamic influence of quantum probing on an object is studied. Here, quantum probing is understood as a pre-measurement based on a non-demolition interaction, which records some information of the probed object, but does not change its energy state when both the probing apparatus and the probed object are isolated from the environment. It is argued that when the probing apparatus and the probed object are immersed in a same equilibrium environment, the probing can affect the effective temperature of the object or induce a quantum isothermal process for the object to transfer its energy. This thermodynamic feature can be regarded as a witness of the existence of quantum probing even if the quantum probing would not disturb the object if the environment were not present.

quant-ph↗

arXiv2009

Quantum switch for single-photon transport in a coupled superconducting transmission line resonator array

We propose and study an approach to realize quantum switch for single-photon transport in a coupled superconducting transmission line resonator (TLR) array with one controllable hopping interaction. We find that the single-photon with arbitrary wavevector can transport in a controllable way in this system. We also study how to realize controllable hopping interaction between two TLRs via a superconducting quantum interference device (SQUID). When the frequency of the SQUID is largely detuned from those of the two TLRs, the variables of the SQUID can be adiabatically eliminated and thus a controllable interaction between two TLRs can be obtained.

quant-ph↗

arXiv2009

Two-Photon Scattering in One Dimension by Localized Two-Level System

We study two-photon scattering in a one-dimensional coupled resonator arrays (CRA) by a two-level system (TLS), which is localized as a quantum controller. The $S$-matrix is analytically calculated for various two-photon scattering processes by TLS, e.g., one photon is confined by TLS to form a bound state while the other is in the scattering state. It is discovered from the poles of the $S$-matrix that there exist two kinds of three-body bound states for describing two bound photons localized around TLS.

quant-ph↗

arXiv2009

One Hair Postulate for Hawking Radiation as Tunneling Process

For Hawking radiation, treated as a tunneling process, the no-hair theorem of black hole together with the law of energy conservation is utilized to postulate that the tunneling rate only depends on the external qualities (e.g., the mass for the Schwarzschild black hole) and the energy of the radiated particle. This postulate is justified by the WKB approximation for calculating the tunneling probability. Based on this postulate, a general formula for the tunneling probability is derived without referring to the concrete form of black hole metric. This formula implies an intrinsic correlation between the successive processes of the black hole radiation of two or more particles. It also suggests a kind of entropy conservation and thus resolves the puzzle of black hole information loss in some sense.

hep-th↗

arXiv2009

Quantum radiations from exciton condensate in Electron-Hole Bilayer Systems

Superfluid has been realized in Helium-4, Helium-3 and ultra-cold atoms. It has been widely used in making high-precision devices and also in cooling various systems. There have been extensive experimental search for possible exciton superfluid (ESF) in semiconductor electron-hole bilayer (EHBL) systems below liquid Helium temperature. However, exciton superfluid are meta-stable and will eventually decay through emitting photons. Here we study quantum nature of photons emitted from the excitonic superfluid (ESF) phase in the semiconductor EHBL and find that the light emitted from the excitonic superfluid has unique and unusual features not shared by any other atomic or condensed matter systems. We show that the emitted photons along the direction perpendicular to the layer are in a coherent state, those along all tilted directions are in a two modes squeezed state. We determine the two mode squeezing spectra, the angle resolved power spectrum, the line shapes of both the momentum distribution curve (MDC) and the energy distribution curve (EDC). From the two photon correlation functions, we find there are photon bunching, the photo-count statistics is super-Poissonian. We discuss how several important parameters such as the chemical potential, the exciton decay rate, the quasiparticle energy spectrum and the dipole-dipole interaction strength between the excitons in our theory can be extracted from the experimental data and comment on available experimental data on both EDC and MDC.

cond-mat.mtrl-sci↗

arXiv2009

Möbius Graphene Strip as Topological Insulator

We study the electronic properties of Möbius graphene strip with a zigzag edge. We show that such graphene strip behaves as a topological insulator with a gapped bulk and a robust metallic surface, which enjoys some features due to its nontrivial topology of the spatial configuration, such as the existence of edge states and the non-Abelian induced gauge field. We predict that the topological properties of the Möbius graphene strip can be experimentally displayed by the destructive interference in the transmission spectrum, and the robustness of edge states under certain perturbations.

cond-mat.mes-hall↗

arXiv2009

Theory of Optically-Driven Sideband Cooling for Atomic Collective Excitations and Its Generalization

We explore how to cool atomic collective excitations in an optically-driven three-level atomic ensemble, which may be described by a model of coupled two harmonic oscillators (HOs) with a time-dependent coupling. Moreover, the coupled two-HO model is further generalized to address other cooling issues, where the lower-frequency HO can be cooled whenever the cooling process dominates over the heating one during the sideband transitions. Unusually, due to the absence of the heating process, the optimal cooling of our first cooling protocol for collective excitations in an atomic ensemble could break a usual sideband cooling limit for general coupled two-HO models.

quant-ph↗

arXiv2009

Recovering Unitarity of Lee Model in Bi-Orthogonal Basis

We study how to recover the unitarity of Lee model with the help of bi-orthogonal basis approach, when the physical coupling constant in renormalization exceeds its critical value, so that the Lee's Hamiltonian is non-Hermitian with respect to the conventional inner product. In a very natural fashion, our systematic approach based on bi-orthogonal basis leads to an elegant definition of inner product with a non-trivial metric, which can overcome all the previous problems in Lee model, such as non-Hermiticity of the Hamiltonian, the negative norm, the negative probability and the non-unitarity of the scattering matrix.

hep-th↗

arXiv2009

Multi-Stability of Electromagnetically Induced Transparency in Atom-Assisted Optomechanical Cavities

We study how an oscillating mirror affects the electromagnetically induced transparency (EIT) of an atomic ensemble, which is confined in a gas cell placed inside a micro-cavity with an oscillating mirror in one end. The oscillating mirror is modeled as a quantum mechanical harmonic oscillator. The cavity field acts as a probe light of the EIT system and also produces a light pressure on the oscillating mirror. The back-action from the mirror to the cavity field results in several (from one to five) steady-states for this atom-assisted optomechanical cavity, producing a complex structure in its EIT. We calculate the susceptibility with respect to the few (from one to three) stable solutions found here for the equilibrium positions of the oscillating mirror. We find that the EIT of the atomic ensemble can be significantly changed by the oscillating mirror, and also that the various steady states of the mirror have different effects on the EIT.

quant-ph↗

arXiv2009

Molecular Ensemble Based Remote Quantum Storage for Charge Qubit via Quasi-Dark State

We propose a quantum storage scheme independent of the current time-control schemes, and study a "quantum data bus" (transmission line resonator) in a hybrid system consisting of a circuit QED system integrated with a cold molecular ensemble. Here, an effective interaction between charge qubit and molecule is mediated by the off-resonate field in the data bus. Correspondingly, the charge state can be mapped into the collective quasi-spin state of the molecular ensemble via the standard dark state based adiabatic manipulation.

quant-ph↗

arXiv2009

On quantum optical properties of single-walled carbon nanotube

We study quantum optical properties of the single-walled carbon nanotube (SWCNT) by introducing the effective interaction between the quantized electromagnetic field and the confined electrons in the SWCNT. Our purpose is to explore the quantum natures of electron transport in the SWCNT by probing its various quantum optical properties relevant to quantum coherence, such as the interference of the scattered and emitted photons, and the bunching and anti-bunching of photons which are characterized by the higher order coherence functions. In the strong field limit, we study the interband Rabi oscillation of electrons driven by a classical light. We also investigate the possible lasing mechanism in superradiation of coherent electrons in a SWCNT driven by a light pump or electron injection, which generate electron population inversion in the higher energy-band of SWCNT.

cond-mat.mes-hall↗

arXiv2009

Non-Adiabatic Fluctuation in Measured Geometric Phase

We study how the non-adiabatic effect causes the observable fluctuation in the "geometric phase" for a two-level system, which is defined as the experimentally measurable quantity in the adiabatic limit. From the Rabi's exact solution to this model, we give a reasonable explanation to the experimental discovery of phase fluctuation in the superconducting circuit system [P. J. Leek, \textit{et al}., Science \textbf{318}, 1889 (2007)], which seemed to be regarded as the conventional experimental error.

quant-ph↗