arXiv subjects

Fu-li Li

Publications and source records attributed to Fu-li Li.

At least 19 recordsLinked to original sources

arXiv2023

Chiral cavity-magnonic system for the unidirectional emission of a tunable squeezed microwave field

Unidirectional photon emission is crucial for constructing quantum networks and realizing scalable quantum information processing. In the present work an efficient scheme is developed for the unidirectional emission of a tunable squeezed microwave field. Our scheme is based on a chiral cavity magnonic system, where a magnon mode in a single-crystalline yttrium iron garnet (YIG) sphere is selectively coupled to one of the two degenerate rotating microwave modes in a torus-shaped cavity with the same chirality. With the YIG sphere driven by a two-color Floquet field to induce sidebands in the magnon-photon coupling, we show that the unidirectional emission of a tunable squeezed microwave field can be generated via the assistance of the dissipative magnon mode and a waveguide. Moreover, the direction of the proposed one-way emitter can be controlled on demand by reversing the biased magnetic field. Our work opens up an avenue to create and manipulate one-way nonclassical microwave radiation field and could find potential quantum technological applications.

quant-ph↗

arXiv2023

Enhancing strength and range of atom-atom interaction in a coupled-cavity array via parametric drives

Coherent long-range interactions between atoms are a prerequisite for numerous applications in the field of quantum information science, but they usually decrease exponentially with the increase in atomic separation. Here we present an appealing method to dramatically enhance the long-range atom-atom interaction mediated by a coupled-cavity array that is subjected to two-photon (parametric) drives. Our method allows one to greatly amplify both the localization length of the single-photon bound-state wavefunction and the effective atom-photon coupling strength, resulting in a significant improvement of photon-mediated coherent interaction between two distant atoms. Additionally, we illustrate this effect by analyzing how it facilitates the transfer of information and the creation of entanglement between the atoms.

quant-ph↗

arXiv2023

Investigation of the laser-induced lineshape change in attosecond transient absorption spectra by employing a time-dependent generalized Floquet approach

We introduce a time-dependent generalized Floquet (TDGF) approach to calculate attosecond transient absorption spectra of helium atoms subjected to the combination of an attosecond extreme ultraviolet (XUV) pulse and a delayed few-cycle infrared (IR) laser pulse. This TDGF approach provides a Floquet understanding of the laser-induced change of resonant absorption lineshape. It is analytically demonstrated that, the phase shift of the time-dependent dipole moment that results in the lineshape changes consists of the \emph{adiabatic} laser-induced phase (LIP) due to the IR-induced stark shifts of adiabatic Floquet states and the \emph{non-adiabatic} phase correction due to the non-adiabatic IR-induced coupling between adiabatic Floquet states. Comparisons of the spectral lineshape calculated based on the TDGF approach with the results obtained with the LIP model [S. Chen \emph{et al.}, Phys. Rev. A \textbf{88}, 033409(2013)] and the rotating-wave approximation (RWA) are made in several typical cases. It is suggested in the picture of adiabatic Floquet states that, the LIP model works as long as the generalized adiabatic theorem [A. Dodin \emph{et al.}, Phys. Rev. X Quantum \textbf{2}, 030302(2021)] fulfils, and the RWA works when the higher-order IR-coupling effect in the formation of adiabatic Floquet states is neglectable.

physics.optics↗

arXiv2022

Chiral coupling between a ferromagnetic magnon and a superconducting qubit

Chiral coupling at the single-quantum level promises to be a remarkable potential for quantum information processing. Here we propose to achieve a chiral interaction between a magnon mode in a ferromagnetic sphere and a superconducting qubit mediated by a one-dimensional coupled-cavity array. When the qubit is coupled to two lattice sites of the array and each one is encoded with a tunable phase, we can acquire a directional qubit-magnon interaction via the quantum interference effect. This work opens up a new route to construct chiral devices, which are expected to become a building block in quantum magnonic networks.

cond-mat.mes-hall↗

arXiv2022

Photon-pair blockade in a Josephson-photonics circuit with two nondegenerate microwave resonators

We propose to generate photon-pair blockade in a Josephson-photonics circuit that consists of a dc voltage-biased Josephson junction in series with a superconducting charge qubit and two nondegenerate microwave resonators. The two-level charge qubit is utilized to create anticorrelations of the charge transport; that is, the simultaneous Cooper pair tunneling events are inhibited. When the Josephson frequency matches the sum of resonance frequencies of the charge qubit and the two resonators, we demonstrate that the two resonators can release their energies in the form of antibunched pairs of two strongly correlated photons. The present work provides a practical way for producing a bright microwave source of antibunched photon pairs, with potential applications ranging from spectroscopy and metrology to quantum information processing.

quant-ph↗

arXiv2018

Experimental observation of three-photon superbunching in linear optical system

Three-photon superbunching is experimentally observed with the recently proposed superbunching pseudothermal light. To the best of our knowledge, it is the first time that three-photon superbunching is observed in linear optical system. From the quantum optics point of view, three-photon superbunching is interpreted as the result of constructive-destructive three-photon interference. The key to observe three-photon superbunching in superbunching pseudothermal light is that all the different ways to trigger a three-photon coincidence count are in principle indistinguishable, which is experimentally guaranteed by putting a pinhole before each rotating groundglass to ensure that all the passed photons are within one coherence area. The observed three-photon superbunching is helpful to increase the visibility of ghost imaging and understand the physics of third-order interference of light.

quant-ph↗

arXiv2018

Superbunching pseudothermal light with intensity modulated laser light and rotating groundglass

Pseudothermal light by scattering laser light from rotating groundglass has been extensively employed to study optical coherence in both classical and quantum optics ever since its invention in 1960s. In this paper, we will show that by replacing the invariant intensity laser light in pseudothermal light source with intensity modulated laser light, superbunching pseudothermal light can be obtained. Two-photon interference in Feynman's path integral theory is employed to interpret the phenomenon. Two-photon superbunching is experimentally observed by employing common instruments in optical laboratory. The proposed superbunching pseudothermal light is helpful to understand the physics of two-photon bunching and superbunching, and the difference between classical and quantum interpretations of the second- and higher-order interference of light.

quant-ph↗

arXiv2017

High visibility temporal ghost imaging with classical light

High visibility temporal ghost imaging with classical light is possible when superbunching pseudothermal light is employed. In the numerical simulation, the visibility of temporal ghost imaging with pseudothermal light equaling ($4.7\pm 0.2$)\% can be increased to ($75\pm 8$)\% in the same scheme with superbunching pseudothermal light. The reasons for the difference in visibility and quality of the retrieved images in different situations are discussed in detail. It is concluded that high visibility and high quality temporal ghost image can be obtained by collecting large enough number of data points. The results are helpful to understand the difference between ghost imaging with classical light and entangled photon pairs. The superbunching pseudothermal light can be employed to improve the image quality in ghost imaging applications.

quant-ph↗

arXiv2017

Superbunching pseudothermal light

A novel and simple superbunching pseudothermal light source is introduced based on common instruments such as laser, lens, pinhole and groundglass. $g^{(2)}(0)=3.66 \pm 0.02$ is observed in the suggested scheme by employing two rotating groundglass. Quantum and classical theories are employed to interpret the observed superbunching effect. It is predicted that $g^{(2)}(0)$ can reach $2^N$ if $N$ rotating groundglass were employed. These results are helpful to understand the physics of superbunching. The proposed superbunching pseudothermal light may serve as a new type of light to study the second- and higher-order coherence of light and have potential application in improving the visibility of thermal light ghost imaging.

quant-ph↗

arXiv2016

Fermionic ghost imaging

Ghost imaging with thermal fermions is calculated based on two-particle interference in Feynman's path integral theory. It is found that ghost imaging with thermal fermions can be simulated by ghost imaging with thermal bosons and classical particles. Photons in pseudothermal light are employed to experimentally study fermionic ghost imaging. Ghost imaging with thermal bosons and fermions is discussed based on the point-to-point (spot) correlation between the object and image planes. The employed method offers an efficient guidance for future ghost imaging with real thermal fermions, which may also be generalized to study other second-order interference phenomena with fermions.

quant-ph↗

arXiv2016

Second-order Fermionic Interference with Independent Photons

The experimental study of the second-order interference with fermions is much less than the one with bosons since it is much more difficult to do experiments with fermions than with photons. Based on the conclusion that the behavior of two identical classical particles has exactly half fermionic and half bosonic characteristics (PRA \textbf{88}, 012130 (2013)), we have studied the second-order interference of fermions via the second-order interference of photons in Hanbury Brown-Twiss and Hong-Ou-Mandel interferometers, respectively. The experimental results are consistent with the theoretical predictions, which serve as an efficient guidance for the future interference experiments with fermions. The employed method offers an interesting and convenient way to study the coherence of fermions.

quant-ph↗

arXiv2015

Tunable electromagnetically induced transparency with a coupled superconducting system

Electromagnetically induced transparency (EIT) has usually been demonstrated by using three-level atomic systems. In this paper, we theoretically proposed an efficient method to realize EIT in microwave regime through a coupled system consisting of a flux qubit and a superconducting LC resonator with relatively high quality factor. In the present composed system, the working levels are the dressed states of a two-level flux qubit and the resonators with a probe pump field. There exits a second order coherent transfer between the dressed states. By comparing the results with those in the conventional atomic system we have revealed the physical origin of the EIT phenomenon in this composed system. Since the whole system is artificial and tunable, our scheme may have potential applications in various domains.

quant-ph↗

arXiv2015

Two-photon interference with two independent and tunable single-mode continuous-wave lasers

The second-order temporal interference between two independent single-mode continuous-wave lasers is discussed by employing two-photon interference in Feynman's path integral theory. It is concluded that whether the second-order temporal interference pattern can be retrieved via two-photon coincidence counting measurement is dependent on the relationship between the resolution time of the detection system and the frequency difference between these two lasers. Two identical and tunable single-mode diode lasers are employed to verify the predictions experimentally. The experimental results are consistent with the theoretical predictions. These studies are helpful to understand the physics of two-photon interference with photons of different spectrums and application of two-photon interference in quantum information processing.

physics.optics↗

arXiv2014

The first- and second-order temporal interference between thermal and laser light

The first- and second-order temporal interference between two independent thermal and laser light beams is discussed by employing the superposition principle in Feynman's path integral theory. It is concluded that the first-order temporal interference pattern can not be observed by superposing thermal and laser light, while the second-order temporal interference pattern can be observed in the same condition. These predictions are experimentally verified by employing pseudothermal light to simulate thermal light. The conclusions and method in the paper can be generalized to any order interference of light or massive particles, which is helpful to understand the physics of interference.

physics.optics↗

arXiv2014

Preparing ground states and squeezed states of nanomechanical cantilevers by fast dissipation

We propose a protocol that enables strong coupling between a flux qubit and the quantized motion of a magnetized nanomechanical cantilever. The flux qubit is driven by microwave fields with suitable parameters to induce sidebands, which will lead to the desired coupling. We show that the nanomechanical modes can be cooled to the ground states and the single-mode squeezed vacuum states can be generated via fast dissipation of the flux qubit. In our scheme, the qubit decay plays a positive role and can help drive the system to the target states.

quant-ph↗

arXiv2013

Control excitation and coherent transfer in a dimer

In this article, the processes of energy absorption and coherent transfer in a dimer is studied. The dimer includes two two-level pigments --- donor and acceptor, where donor is assumed being excited by a control pulse in the time domain. We investigate the dynamics of probability that the acceptor is in the excited state and the total efficiency of energy absorption and transfer under different temporal shape of control pulse. Quantum concurrence of the dimer is also discussed.

quant-ph↗

arXiv2011

Enhancement of non-equilibrium thermal quantum discord and entanglement of a three-spin XX chain by multi-spin interaction and external magnetic field

We investigate the non-equilibrium thermal quantum discord and entanglement of a three-spin chain whose two end spins are respectively coupled to two thermal reservoirs at different temperatures. In the three-spin chain, besides the XX-type nearest-neighbor two-spin interaction, a multi-spin interaction is also considered and a homogenous magnetic field is applied to each spin. We show that the extreme steady-state quantum discord and entanglement of the two end spins can always be created by holding both a large magnetic field and a strong multi-spin interaction. The results are explained by the thermal excitation depression due to switching a large energy gap between the ground state and the first excited state. The present investigation may provide a useful approach to control coupling between a quantum system and its environment.

quant-ph↗

arXiv2010

Controlling transfer of quantum correlations among bi-partitions of a composite quantum system by combining noisy environments

The correlation dynamics is investigated for various bi-partitions of a composite system consisting of two qubits, and two independent and non-identical noisy environments. The two qubits have no direct interaction with each other and locally interact with their environments. Classical and quantum correlations including entanglement are initially prepared only between the two qubits. We find that, contrary to the identical noisy environment case, the entanglement and quantum correlation transfer directions can be controlled by combining different noisy environments. The amplitude damping environment determines whether there exists entanglement transfer among the bi-partitions of a composite system. When one qubit is coupled to an amplitude damping environment but another one to a bit-flip one, we find a very interesting result that all the quantum and classical correlations, and even the entanglement, originally existing between the qubits, can be completely transferred without any loss to the qubit coupled to the bit-flip environment and the amplitude-damping environment. We also notice that it is possible to distinguish the quantum correlation from the classical correlation and entanglement by combining different noisy environments.

quant-ph↗