Nonclassical Photon Statistics Research Articles

Anisotropic qubit-photon interactions inducing multiple antibunching-to-bunching transitions of photons

We investigate photon correlations in the open anisotropic quantum Rabi model via quantum dressed master equation. Multiple antibunching-to-bunching transitions are generally exhibited at deep-strong qubit-photon coupling, which becomes vanishing in the standard open quantum Rabi model. The observed two-photon statistics can be well described analytically within a few lowest eigenstates at low temperatures. It is revealed that the additional photon antibunching effect mainly originates from the selection rule of the correlation-measurement-induced eigenstate transitions. Furthermore, we also unravel the phenomena that higher-order correlation function lifts up dramatically once passing the crossing point of excited states, which is attributed to the on-off switch of dominant cooperative transition with level crossing. We hope these results may fertilize the analysis of the nonclassical photon statistics in anisotropic coupled qubit-photon systems.

Storage of telecom wavelength heralded single photons in a fiber cavity quantum memory

We demonstrate the storage and retrieval of heralded single photons in a fiber-based cavity quantum memory. The photons are stored, and retrieved, from the memory using quantum frequency conversion which switches the photon into, and out of, resonance with the cavity. The photons, generated in the telecom O-band with a bandwidth of 81 GHz, are retrieved from the memory with a 1/e lifetime of 1.64 µs, or 32.8 cavity round trips. We show that non-classical photon statistics remain for 70 round trips. The internal memory efficiency after 0.5 µs of storage is 10.9 ± 0.5%; a coupling efficiency of 60% into the memory cavity yields a total efficiency of 6.0 ± 0.3%. These results mark a crucial step forward in the development of fiber-based quantum memories, and high-bandwidth memories operating at telecom wavelengths, with applications to photon source multiplexing and fiber-based quantum networking.

A multiplexed synthesizer for non-Gaussian photonic quantum state generation

Disposing of simple and efficient sources for photonic states with non-classical photon statistics is of paramount importance for implementing quantum computation and communication protocols. In this work, we propose an innovative approach that drastically simplifies the preparation of non-Gaussian states as compared to previous proposals, by taking advantage from the multiplexing capabilities offered by modern quantum photonics tools. Our proposal is inspired by iterative protocols, where multiple resources are combined one after the other for obtaining high-amplitude complex output states. Here, conversely, a large part of the protocol is performed in parallel, by using a single projective measurement along a mode which partially overlaps with all the input modes. We show that our protocol can be used to generate high-quality and high-amplitude Schrödinger cat states as well as more complex states such as error-correcting codes. Remarkably, our proposal can be implemented with experimentally available resources, highlighting its straightforward feasibility.

Creation of nonclassical states of light in a chiral waveguide

Creating nonclassical states of light from simple quantum systems together with classical resources is a challenging problem. We show how chiral emitters under a coherent drive can generate nonclassical photon states. For our analysis, we select a specific temporal mode in the transmitted light field, resulting in a coupled master equation for the relevant mode and the chiral emitters. We characterize the mode's state by its Wigner function and show that the emission from the system predominantly produces mixtures of few-photon-added coherent states. We argue that these nonclassical states are experimentally accessible and show their application for quantum metrology.

Nonclassical photon statistics and photon squeezing in the dissipative mixed quantum Rabi model

Nonclassical two-photon statistics and photon squeezing are considered as representative features of the nonclassicality of light. In this work we investigate two-photon correlation function and quadrature photon squeezing in the dissipative mixed quantum Rabi model (QRM), which includes both the one-photon and two-photon qubit–resonator interactions. The quantum dressed master equation combined with squeezed-coherent states is applied to obtain the steady state. Based on the zero-time delay two-photon correlation function, it is found that with the increase of the two-photon qubit–resonator interaction strength the photon antibunching behavior is monotonically suppressed, whereas the photon bunching signature persists. One additional giant photon bunching feature is unraveled at deep-strong two-photon coupling, which mainly stems from efficient successive transition trajectories. The finite-time delay two-photon correlation function asymptotically approaches the unit by raising the delayed time. Moreover, the steady-state quadrature photon squeezing becomes significant at strong two-photon coupling, which may become perfect in the zero temperature limit.

Nonclassical photon statistics in two-tone continuously driven optomechanics

In cavity optomechanics, single photon detection of Raman scattered photons can be a useful tool for observing nonclassical features of both radiation and motion. While this tool has been employed in experiments with pulsed laser driving of a cavity mode, it has not been readily accessible to experiments with continuous and constant laser driving. To address this, we present a study of a standard optomechanical system where the cavity mode is continuously driven at two different frequencies, and where sideband photons are detected by single photon detectors after frequency filtering the output from the cavity mode around its resonance frequency. We first derive the normalized second order coherence associated with the detected photons, and show that it contains signatures of the quantum nature of the mechanical mode which would be absent with only single-tone driving. To identify model-independent nonclassical features, we derive two inequalities for the sideband photon statistics that should be valid in any classical model of the system. We show that these inequalities are violated in the proposed setup. This is provided that the average phonon occupation number of the mechanical mode is sufficiently small, which in principle can be achieved through sideband cooling intrinsic to the setup. Violation of the first inequality means that there is no well-defined probability distribution of the Glauber-Sudarshan type for the cavity mode. In contrast, a violation of the second inequality means that there is no joint probability distribution for the cavity mode at two times separated by a finite interval, which originates from the noncommutativity of the motional quadratures of the mechanical mode. The proposed setup thus employs a mechanical oscillator in order to generate a steady-state source of nonclassical radiation.

Bayesian inference for plasmonic nanometrology

We introduce a Bayesian method for the characterization of plasmonic nanoparticles, which is applicable to both near- and far-field problems. Designed to combine data generated from any photon-plasmon interaction experiment with physically motivated theoretical models, our approach leverages state-of-the-art Markov chain Monte Carlo sampling techniques and returns parameter estimates on nanometric scales. Simulated spectral data sets, describing resonant scattering of photons from ellipsoidal and toroidal nanoparticles, are explored as concrete examples of our approach, with the resulting Bayesian estimates showing excellent agreement with the ground truth, even under conditions of high statistical noise. By incorporating Bayes factors into the method as well, we reveal how model selection can determine which one of competing geometric shapes better explains the observed data. Our comprehensive nanometrology procedure can be tailored to a variety of light-particle interaction models, and its reliance on Bayesian inference furnishes automatic uncertainty quantification. In addition to applicability to a host of plasmonic configurations such as nanoparticle dimers, trimers, and array studies, it is proposed that the presented analysis can be extended to the quantum regime, where nonclassical photon statistics may provide additional insight for inference of scatterer properties.

Optical feedback-induced dynamics and nonclassical photon statistics of semiconductor microcavity laser

We study a coherently driven semiconductor laser cavity containing a single quantum dot(QD) (as gain medium) with optical feedback under Markovian approximation. We have obtained coupled operator equations for the model Hamiltonian using standard input-output formalism of cavity-QED and have found that these equations do not have any finite steady state solutions. We have also used an exact numerical framework based on Matlab platform qotoolbox, to compute the temporal dynamics of the mean excitation number of laser cavity mode under high feedback coupling regime. We have further studied the photon correlations of both the cavity mode as well as external feedback mode to feedback identify the laser parameters and coupling strength that give the nonclassical sub-Poissonian photon statistics. This work is useful for coherent control of photon statistics and photon correlations in the semiconductor laser with optical feedback.

Enhancing photoelectric current by nonclassical light

We study the photoelectric current generated by a driving light with nonclassical photon statistics. Due to the nonclassical input photon statistics, it is no longer enough to treat the driving light as a planar wave as in classical physics. We make a quantum approach to study such problems, and find that: when the driving light starts from a coherent state as the initial state, our quantum treatment well returns the quasi-classical driving description; when the the driving light is a generic state with a certain P function, the full system dynamics can be reduced as the P function average of many ‘branches’—in each dynamics branch, the driving light starts from a coherent state, thus again the system dynamics can be obtained in the above quasi-classical way. Based on this quantum approach, it turns out the different photon statistics does make differences to the photoelectric current. Among all the classical light states with the same light intensity, we prove that the input light with Poisson statistics generates the largest photoelectric current, while a nonclassical sub-Poisson light could exceed this classical upper bound.

Nonclassical photon statistics and bipartite entanglement generation of excited coherent states

We have studied the effect of a beam splitter on the excited coherent states, which are an intermediate state between the fock state and the coherent state. These states are obtained due to successive elementary one-photon excitations of a coherent state. We have used linear entropy to measure the entanglement generated through a beam splitter when a single-mode excited coherent state is injected at each input port of the beam splitter. We have used our very generalized results to study the possible generation of entanglement for few more specific cases also. Furthermore, we have also studied the nonclassical photon statistics of the output field through the Mandel’s Q parameter and have found the correlation between the photon statistics and the entanglement of the output state.

Generation of non-classical states of photons from a metal-dielectric interface: a novel architecture for quantum information processing.

We show the possibility to generate photons in a certain class of non-classical states from a metal-dielectric interface using dipole emitters on the interface. The photons emitted into the surface plasmon mode from the initially excited emitters radiate out in free space in a cone-shaped geometry. When detected at two detectors, these photons exhibit coalescence, a clear signature of non-classicality. Such a system can also be employed as a building block for a distributed quantum network. We further show that it is indeed feasible to implement our model using available technology.

Direct Measurement of Non-Classical Photon Statistics with a Multi-Pixel Photon Counter

Photon number resolving detectors with high accuracy bring broad applications in long-distance laser ranging, ultrafast spectroscopy, and quantum optics. In this paper, we observed the non-classical photon number distribution directly with a multi-pixel photon counter (MPPC) instead of a classic Hanbury-Brown and Twiss (HBT) system. The detector’s photon-number resolving ability was characterized by quantum detector tomography. To show the quantum feature of the detector, we further plotted the Wigner function, which was obtained corresponding to the positive operator value measure (POVM) elements. Finally, we declared the observation of non-classical photon statistics from a single color center in nanodiamond by using this detector.

Formation of non-classical optical states in spaser systems under control of an external magnetic field

The work is focused on the investigation of features of quantum dynamics for photons in spaser systems consisting of metal nanoparticles (NP) and semiconductor quantum dots (QDs). The non-classical photon states generation in a three-particle spaser system with nonlinear plasmon-exciton interaction is predicted.

Quantum dynamics and nonclassical photon statistics of coherently driven Raman transition in bimodal cavity

ABSTRACTWe study a classically driven two-level system in a harmonic trap and a lossy two-mode cavity, with the first mode being resonant to the driving field and an electronic transition, and the second mode being off-resonant, forming a vibrational-assisted Raman transition. Using an exact numerical method, we compute the steady state as well as the time evolution of the photon statistics. We further investigate the photon correlations of both the cavity modes and identify the laser parameters and coupling strength that give the nonclassical sub-Poissonian property. The work is useful for coherent control of photon statistics and photon correlations in the trapped two-level system.

Long-Distance Single Photon Transmission from a Trapped Ion via Quantum Frequency Conversion.

Trapped atomic ions are ideal single photon emitters with long-lived internal states which can be entangled with emitted photons. Coupling the ion to an optical cavity enables the efficient emission of single photons into a single spatial mode and grants control over their temporal shape. These features are key for quantum information processing and quantum communication. However, the photons emitted by these systems are unsuitable for long-distance transmission due to their wavelengths. Here we report the transmission of single photons from a single ^{40}Ca^{+} ion coupled to an optical cavity over a 10km optical fiber via frequency conversion from 866nm to the telecom C band at 1530nm. We observe nonclassical photon statistics of the direct cavity emission, the converted photons, and the 10km transmitted photons, as well as the preservation of the photons' temporal shape throughout. This telecommunication-ready system can be a key component for long-distance quantum communication as well as future cloud quantum computation.

Quantum correlation enhanced super-resolution localization microscopy enabled by a fibre bundle camera

Despite advances in low-light-level detection, single-photon methods such as photon correlation have rarely been used in the context of imaging. The few demonstrations, for example of subdiffraction-limited imaging utilizing quantum statistics of photons, have remained in the realm of proof-of-principle demonstrations. This is primarily due to a combination of low values of fill factors, quantum efficiencies, frame rates and signal-to-noise characteristic of most available single-photon sensitive imaging detectors. Here we describe an imaging device based on a fibre bundle coupled to single-photon avalanche detectors that combines a large fill factor, a high quantum efficiency, a low noise and scalable architecture. Our device enables localization-based super-resolution microscopy in a non-sparse non-stationary scene, utilizing information on the number of active emitters, as gathered from non-classical photon statistics.

Double-resonance response of a superconducting quantum metamaterial: Manifestation of nonclassical states of photons

We report a theoretical study of ac response of superconducting quantum metamaterials (SQMs), i.e. an array of qubits (two-levels system) embedded in the low-dissipative resonator. By making use of a particular example of SQM, namely the array of charge qubits capacitively coupled to the resonator, we obtain a second-order phase transition between an incoherent (the high-temperature phase) and coherent (the low-temperatures phase) states of photons. This phase transition in many aspects resembles the paramagnetic-ferromagnetic phase transition. The critical temperature of the phase transition, $T^\star$, is determined by the energy splitting of two-level systems $\delta$, number of qubits in the array $N$, and the strength of the interaction $\eta$ between qubits and photons in the cavity. We obtain that the photon states manifest themselves by resonant drops in the frequency dependent transmission $D(\omega)$ of electromagnetic waves propagating through a transmission line weakly coupled to the SQM. At high temperatures the $D(\omega)$ displays a single resonant drop, and at low temperatures a peculiar \emph{double resonance response} has to be observed. The physical origin of such a resonant splitting is the quantum oscillations between two coherent states of photons of different polarizations.

Strain Coupling of a Mechanical Resonator to a Single Quantum Emitter in Diamond

The recent maturation of hybrid quantum devices has led to significant enhancements in the functionality of a wide variety of quantum systems. In particular, harnessing mechanical resonators for manipulation and control has expanded the use of two-level systems in quantum information science and quantum sensing. In this letter, we report on a monolithic hybrid quantum device in which strain fields associated with resonant vibrations of a diamond cantilever dynamically control the optical transitions of a single nitrogen-vacancy (NV) defect center in diamond. We quantitatively characterize the strain coupling to the orbital states of the NV center, and with mechanical driving, we observe NV-strain couplings exceeding 10 GHz. Furthermore, we use this strain-mediated coupling to match the frequency and polarization dependence of the zero-phonon lines of two spatially separated and initially distinguishable NV centers. The experiments demonstrated here mark an important step toward engineering a quantum device capable of realizing and probing the dynamics of non-classical states of mechanical resonators, spin-systems, and photons.

Generating nonclassical photon states via longitudinal couplings between superconducting qubits and microwave fields

Besides the conventional transverse couplings between superconducting qubits (SQs) and electromagnetic fields, there are additional longitudinal couplings when the inversion symmetry of the potential energies of the SQs is broken. We study nonclassical-state generation in a SQ which is driven by a classical field and coupled to a single-mode microwave field. We find that the classical field can induce transitions between two energy levels of the SQs, which either generate or annihilate, in a controllable way, different photon numbers of the cavity field. The effective Hamiltonians of these classical-field-assisted multiphoton processes of the single-mode cavity field are very similar to those for cold ions, confined to a coaxial RF-ion trap and driven by a classical field. We show that arbitrary superpositions of Fock states can be more efficiently generated using these controllable multiphoton transitions, in contrast to the single-photon resonant transition when there is only a SQ-field transverse coupling. The experimental feasibility for different SQs is also discussed.

Temporal Dynamics and Nonclassical Photon Statistics of Quadratically Coupled Optomechanical Systems

Quantum optomechanical system serves as an interface for coupling between photons and phonons due to mechanical oscillations. We used the Heisenberg-Langevin approach under Markovian white noise approximation to study a quadratically coupled optomechanical system which contains a thin dielectric membrane quadratically coupled to the cavity field. A decorrelation method is employed to solve for a larger number of coupled equations. Transient mean numbers of cavity photons and phonons that provide dynamical behaviour are computed for different coupling regime. We have also obtained the two-boson second-order correlation functions for the cavity field, membrane oscillator and their cross correlations that provide nonclassical properties governed by quadratic optomechanical system.