Single-photon Transport Research Articles

Single-photon pulse transport in a waveguide coupled with a quantum system

We study the transmission and reflection properties of a single-photon pulse in a one-dimensional waveguide side coupled with a Jaynes-Cummings system, namely, a multi-cavity with an embedded Rydberg atom. A Single-photon pulse is applied to tune the atoms energy spectrum, and varying it can bring the atomic qubit transition on or off-resonance for the cavity. The transmission and reflection behavior are systematically explored by a real-space model Hamiltonian and we find that the coupling strength between the waveguide and the side optical cavity exerts a tremendous impact on it. The influence of cavity and atomic dissipations and the incident pulse width on the transport properties of the single-photon is also investigated simultaneously. Based on these phenomena, we point out the possibility of utilizing this system as a single-photon transport in practice and has potential applications in quantum information.

Designable quantum beamsplitter using the two-level InGaAs quantum dot interacting with a Y-Type plasmonic waveguide

We have theoretically studied the designable quantum beamsplitter of single photons interacting with the two-level quantum dot placed in the node of a Y-type waveguide on the basis of the real-space approach. We showed that splitting of incoming single photons from one quantum channel to the others could be achieved by controlling the coupling strength of two-level quantum dot with waveguide, detuning between the quantum dot and the incoming single photon, and so on. Such quantum devices based on the controllable single photon transport behave as quantum beamsplitter at the single photon level, which provides us rich ways of configuration of important elements for the practical realization of the quantum information network.

Single-Photon Transport in a Topological Waveguide from a Dynamically Modulated Photonic System

The topologically protected one-way edge modes for light show a way to manipulate the interaction between a single photon and a quantum emitter. We systematically study single-photon quantum optics in a topological waveguide supporting the frequency-dependent one-way edge mode at the boundary of a dynamically modulated photonic system, and compare the results of the single-photon interacting dynamics with the quantum emitter in a unidirectional waveguide. As a major difference, a photon in a topological waveguide propagates around the resonant site coupled to the quantum emitter due to the topological protection. Our results show that, despite different subtleties, photon-emitter interactions for one photon at the edge mode and for one photon propagating in a unidirectional waveguide hold similar features. In addition, we consider the interaction between the photon and a $\mathrm{\ensuremath{\Lambda}}$-type three-level quantum emitter in the topological waveguide, where we show the nonlocal correlated photon-state generation as well as the single-photon reflection with the frequency conversion. Our work provides insight for understanding the interaction between the topologically protected unidirectional-propagating photon and the quantum emitter, which holds promise for potential applications in quantum-information processing.

Frequency Manipulations in Single-Photon Quantum Transport under Ultrastrong Driving

All-optical manipulation of a single-photon quantum transport is of fundamental importance in quantum nanophotonics. Here, a system consisting of a single-mode waveguide coupling with a V-type thre...

Single-Photon Transport in One-Dimensional Coupled-Resonator Waveguide with Second-Order Nonlinearity oupling to a Nanocavity Containing a Two-Level Atom and Kerr-Nonlinearity

We study controllable single photon scattering in a one-dimensional waveguide coupling with an additional cavity by second order nonlinear materials in a non-cascading configuration, where the additional cavity is embedded with two-level atom and filled with Kerr-nonlinear materials. Considering the second order nonlinear coupling, we analyze the transmission properties of the three different coupling forms as follows: (i) The two-level atom is excited without the Kerr-nonlinearity. (ii)The Kerr-nonlinearity is excited without the two-level atom. (iii) Both of the two-level atom and Kerr-nonlinearity are excited. The transmission and reflection amplitudes are obtained by the discrete coordinates approach for the three cases. The results showed that the transmission properties can be adjusted by the above three different coupling forms, which indicate our scheme can be used as a single photon switch to control the transmission and reflection of the single photon in the one-dimensional coupled resonant waveguide. We compared the results with [Phys. Rev. A 85, 053840(2012)] and find the advantages.

Transparency in a chain of disparate quantum emitters strongly coupled to a waveguide

We demonstrate the emergence of transparent behavior in a chain of periodically spaced non-identical quantums emitters coupled to a waveguide, in the special case when the inter-atomic separation is a half-integral multiple of the resonant wavelength, i.e. $kL$ is an integral multiple of $\pi$, with $k$ being the spatial frequency and $L$ the spatial periodicity. When equal but opposite frequency detunings are assigned in pairs to a system of even number of atoms, perfect transmission ensues. When the chain size is odd, a similar assignment leads to the disappearance of collective effects as the odd atom determines the spectral behavior. We also manifest the robustness of these features against dissipative effects and show, how the spectral behavior hinges significantly on the relative detunings between the atoms as compared to the decay rate. A key distinction from the phenomenon of Electromagnetically Induced Transparency (EIT) is that in the waveguide case, the presence of an intrinsic waveguide mediated phase coupling between the atoms strongly affects the transport properties. Furthermore, while reciprocity in single-photon transport does not generally hold due to the phase coupling, we observe an interesting exception for $kL = n\pi$ at which the waveguide demonstrates reciprocal behavior with regard to both the transmission and reflection coefficients.

Single-photon scattering controlled by an imperfect cavity**Project supported by the National Natural Science Foundation of China (Grant Nos. 11834005 and 11674285).

We study the single-photon transport in the coupled-resonator waveguide (CRW) controlled by an imperfect cavity. A Lorentzian spectrum is introduced to describe the dissipation. We find that the probability current conservation can be broken, although the imperfect cavity is a Hermitian system. The coupling strength between the imperfect cavity and the CRW has significant influences near the resonant frequency. With the increase of the coupling strength, the transmission coefficient becomes smaller. The spectral width plays a dominant role under the off-resonant condition, where the transmission coefficient is greatly suppressed with the increase of the spectral width. We also observe an abrupt jump of the transmission and reflection coefficients when the hopping amplitude is large enough. All the distinctive behaviors are closely related to the complex effective potential induced by the imperfect cavity.

Bandgap-assisted quantum control of topological edge states in a cavity

Quantum matter with exotic topological order has potential applications in quantum computation. However, in present experiments, the manipulations on topological states are still challenging. We here propose an architecture for optical control of topological matter. We consider a topological superconducting qubit array with Su-Schrieffer-Heeger (SSH) Hamiltonian which couples to a microwave cavity. Based on parity properties of the topological qubit array, we propose an optical spectroscopy method to observe topological phase transition, i.e., edge-to-bulk transition. This new method can be achieved by designing cavity-qubit couplings. A main purpose of this work is to understand how topological phase transition affects light-matter interaction. We find that topological bandgap plays an essential role on this issue. In topological phase, the resonant vacuum Rabi splitting of degenerate edge states coupling to the cavity field is protected from those of bulk states by the bandgap. In dispersive regime, the cavity induced coupling between edge states is dominant over couplings between edge and bulk states, due to the topological bandgap. As a result, quantum interference between topological edge states occures and enables single-photon transport through boundaries of the topological qubit array. Our work may pave a way for topological quantum state engineering.

Transport and entanglement for single photons in optical waveguide ladders

Transfer and scattering matrix theories are derived for studying single-photon (SP) transport in optical waveguide ladders (OWLs). The OWLs consist of two one-dimensional waveguides connected by Jaynes-Cummings emitters (JCEs) and have two input and two output channels. The von Neumann entropy is introduced to describe the entanglement between the transmitted states from the two output channels. Two types of the OWLs are studied, i.e., the OWLs with two identical waveguides (i-OWLs) and those with two different waveguides (d-OWLs). When the OWLs contain only one JCE, the SP transport behavior in the i-OWLs is the same as that in the d-OWLs. When two JCEs are introduced, the quantum interference among the JCE-scattered waves can lead to the SP jumping with a 100% chance between the waveguides for the i-OWLs, while this is hard for the d-OWLs. As a result, the i-OWLs can serve as a SP router with respect to the d-OWLs. When the number of JCEs increases to a large value (e.g., 16), the transmission probabilities of the two output channels both tend to be 0.25 for the i-OWLs, but zero for d-OWLs. Correspondingly, the entanglements approximate a constant of 1 for the i-OWLs, but of zero for the d-OWLs. It shows that a large number of JCEs can suppress the influence of other system parameters including the SP frequency and JCE loss. Therefore, the i-OWLs with a large number of the JCEs show potential for a SP splitter and entanglement generator.

Multiple Fano interferences due to waveguide-mediated phase coupling between atoms

We examine quantum interference effects due to absorption and emission from multiple atoms coupled to a waveguide and highlight the modifications they entail in regards to single-photon transport properties. A prominent upshot of these interference phenomena is the resonant suppression of the reflection amplitude, which leads to the observation of multiple Fano minima in the reflection spectrum. Such minima determine the points at which transparency is induced in the system. By taking recourse to the real-space Hamiltonian framework, we calculate analytically the reflectivity and transmissivity for a one-dimensional waveguide that evanescently couples to a chain of equally spaced quantum emitters. The inter-emitter spacing relative to the wavelength of the propagating photon, leading to a waveguide-mediated "phase-coupling" between the atoms, is found to fundamentally affect the existence of Fano minima. For a chain of $N$ atoms, the number of minima can be at most $N-1$. However, suitable choices of the phase can suppress the discernibility of the full range of roots in the reflection spectrum. A principal observation for the case of multiple emitters is the emergence of super-Gaussian characteristics close to zero-detuning and consequently, a plateau-shaped broadband spectrum in the region of high reflectivity. For a large chain size, the plateau gets transformed into a flat-topped quasi-rectangular profile in the frequency domain.

Dynamic Manipulation of Single-Photon Transport along a Waveguide by Dipole-Coupled Two-Level Atoms in a Quadratic Optomechanical Cavity

Single-photon transport along a one-dimensional waveguide side coupled to a quadratic optomechanical cavity embedded in two two-level atoms with dipole-dipole interaction (DDI) are explored theoretically. The transmission and reflection amplitudes are derived using a real-space approach. The effects of the optomechanical coupling strength, the DDI, atom-cavity detuning, and atomic dissipation on the single-photon transport properties are analyzed. In single-photon strong-coupling regime, vacuum Rabi-splitting and electromagnetically induced transparency (EIT)-like transmission spectra are observed. It is found that the DDI can shift the reflected resonant points, change the distance and the minima of the two vacuum Rabi-splitting dips, and modify the EIT-like spectra. Therefore, single-photon transport can be well controlled by such a hybrid atom-optomechanical system.

Influence of impurity on the rate of single photon superradiance and photon transport in disordered N qubit chain

We investigate the rate of superradiant emission for a number of artificial atoms (qubits) embedded in a one-dimensional open waveguide. More specifically, we study the 1D (N+1)- qubit chain where N qubits are identical with respect to their excitation frequency Ω but have different rates of spontaneous emission Γn, and a single impurity qubit which is different from N qubits by its excitation frequency ΩP and the rate of spontaneous emission ΓP. We performed exact diagonalization of Hamiltonian and showed that the system has two hybridized collective states one of which accumulates the widths of all qubits. The energy spectrum of these states and corresponding probabilities are investigated as a function of the frequency detuning between the impurity and other qubits in a chain. It is shown that the inclusion of the impurity qubit alters the resonance widths of the system if the total width overlaps the frequency detuning between qubits and the impurity. In this case the resonance widths experience a significant repulsion. The photon transmission through disordered N- qubit chain with the impurity qubit is also considered. It is shown that a single photon transport through this system is described by a simple expression which predicts for specific photon frequency the existence of a complete transmission peak and transparency window between frequencies Ω and ΩP.

Single-Photon Quantum Router With a Three-Level Atom Embedded Within a T-Bulge Structure of Coupled Resonant Waveguide

Photon quantum routing is one of the key elements of the quantum information network and integrated optical devices. In this paper, we theoretically investigate the single-photon transport in an intersection coupled resonant waveguide (CRW), called the T-bulge structure, in which the $$N\hbox {th}$$ cavity of a semi-infinite CRW couples with one point of an infinite CRW via a cascaded three-level atom. By using the discrete coordinates approach, transmission and reflection amplitudes of the propagating single photon in the waveguide are analytically obtained. Two cases that a single photon is incident from the infinite CRW and from semi-infinite CRW are considered, respectively. Based on the theoretical framework, we show that the quantum router function can be realized by directing a single photon incidenting from the semi-infinite CRW to the infinite CRW with the unity probabilities, and the probability of routing single photons from infinite CRW to semi-infinite CRW could reach 0.5. Our study provides a full quantum control scheme of single-photon scattering in T-bulge structure coupled cavity array waveguide.

Tunable single-photon diode by chiral quantum physics

We investigate the single photon scattering by an emitter chirally coupled to a one-dimensional waveguide. The single-photon transport property is essentially different from the symmetrical coupling case. The single photons propagating towards the emitter in opposite directions show different transmission behaviors, which is a manifestation of the single-photon diode. In the ideal chiral coupling case, the transmission probability of the single photon transport in one direction is zero by critical coupling, while in the opposite direction it is unity. The diode works well only when the single-photon frequency meets certain conditions. For a two-level emitter, the diode works well when the single photon is nearly resonant to the emitter. For a $\Lambda $-type three-level emitter, when the single-photon frequency is greatly altered, we can adjust the parameters of the external laser to ensure the diode works well. The latter provides a manner to realize a single-photon switch, in which the single-photon transmission probability can reach zero or unity although the emitter's decay is considered.

Modulating the single-photon transport periodically with two emitters in two one-dimensional coupled cavity arrays

Abstract We theoretically investigate the coherent transport behavior of a single-photon in T-type coupled cavity arrays (CCAs). Firstly, the case two two-level atoms (TLA) located inside two cavities of the incident channel is investigated, with the first TLA fixed at the T node and the second TLA in any position of CCA-a. The results show that the position of the second atom can periodically manipulate the transfer rate, and the single-photon can be completely routed into CCA-b deterministically. Secondly, we consider the two Λ -type three level atom instead of the two-level atom. When the driving field is present, the Fano-resonance can be observed and gradually becomes a double-peak with the increase of the driving field strength. In addition, the Rabi frequency of the first atom can alter the position of the double-peak, while the driving field intensity of the second atom only varies the peak value of the transfer rate, and the maximum probability may be obtained when the Rabi frequencies of the two Λ -type TLA are equal.

Bound states in the continuum in whispering gallery resonators

We report the formation of bound states in the continuum in a whispering gallery resonator coupled to a one-dimensional waveguide. We find that an incident photon wave packet is partially stored in the bound state in the continuum due to a roughness-induced symmetry breaking. We discuss quantum interference effects such as Fano in the transmission spectra and the photonic density of states. The conditions under which the bound state can be accessed through single-photon transport processes are investigated.

Controlling single-photon transport in an optical waveguide coupled to an optomechanical cavity with a Λ-type three-level atom

We theoretically study the single-photon transport along a one-dimensional optical waveguide coupled to an optomechanical cavity containing a Λ-type three-level atom. Our numerical results show that the transmission spectra of the incident photon can be well controlled by such a hybrid atom-optomechanical system. The effects of the optomechanical coupling strength, the classical laser beam applied to the atom, atom-cavity detuning, and atomic dissipation on the single-photon transport properties are analyzed. It is of particular interest that an analogous double electromagnetically induced transparency emerges in the single-photon transmission spectra.

Single-photon transport in an array of quantum emitters with long-range interactions

We investigate photon transport in a waveguide coupled to two-level quantum emitters with long-range interactions. We derive an exact solution for transmission and reflection amplitudes in the framwork of real-space Hamiltonian. Our explicit formula allows for a complete description of photon transport in the presence of N quantum emitters with arbitrary non-local interactions. We apply this approach to single-photon transport in an one-dimensional waveguide coupled to two atoms with dipole-dipole interaction (DDI). Our numerical results confirm the Fano spectrum line shapes as a result of strong DDI, and demonstrate how the split of perfect reflection spectrum and the resonance transmission can be achieved by tuning the photon-atom and the atom-atom interactions.

Influence of disorder on electromagnetically induced transparency in chiral waveguide quantum electrodynamics

We study single photon transport in a one-dimensional disordered lattice of three-level atoms coupled to an optical waveguide. In particular, we study atoms of \Lambda-type that are capable of exhibiting electromagnetically induced transparency (EIT) and separately consider disorder in the atomic positions and transition frequencies. We mainly address the question of how preferential emission into waveguide modes (chirality) can influence the formation of spatially localized states. Our work has relevance to experimental studies of cold atoms coupled to nanoscale waveguides and has possible applications to quantum communications.

Coupled-resonator waveguide perfect transport single-photon by interatomic dipole–dipole interaction

We theoretically investigate single-photon coherent transport in a one-dimensional coupled-resonator waveguide coupled to two quantum emitters with dipole–dipole interactions. The numerical simulations demonstrate that the transmission spectrum of the photon depends on the two atoms dipole–dipole interactions and the photon–atom couplings. The dipole–dipole interactions may change the dip positions in the spectra and the coupling strength may broaden the frequency band width in the transmission spectrum. We further demonstrate that the typical transmission spectra split into two dips due to the dipole–dipole interactions. This phenomenon may be used to manufacture new quantum waveguide devices.