Stefano Mancini, Alessandra Gatti
We study the phenomena that arise in the transverse structure of electromagnetic field impinging on a linear Fabry-Perot cavity with an oscillating end mirror. We find quantum correlations among transverse modes which can be considered as a signature of their entanglement.
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We perform a quantum mechanical analysis of the pendular cavity, using the positive-P representation, showing that the quantum state of the moving mirror, a macroscopic object, has noticeable effects on the dynamics. This system has previously been proposed as a candidate for the quantum-limited measurement of small displacements of the mirror due to radiation pressure, for the production of states with entanglement between the mirror and the field, and even for superposition states of the mirror. However, when we treat the oscillating mirror quantum mechanically, we find that it always oscill…
Transits of single atoms through higher-order Hermite-Gaussian transverse modes of a high-finesse optical cavity are observed. Compared to the fundamental Gaussian mode, the use of higher-order modes increases the information on the atomic position. The experiment is a first experimental step towards the realisation of an atomic kaleidoscope.
Free-space coupling and characterization of transverse bulk phonon modes in lithium niobate in a quantum acoustic device
该研究通过三维微波腔与Y切铌酸锂衬底中横向体声子的自由空间耦合实现激发与表征，验证了耦合强度、偏振特性及取向依赖性，展示了3D微波腔在非接触耦合压电声学器件中的通用性。
We present an investigation of the coherent coupling of various transverse field modes of an optical cavity to ion Coulomb crystals. The obtained experimental results, which include the demonstration of identical collective coupling rates for different transverse modes of a cavity field to ions in the same large Coulomb crystal, are in excellent agreement with theoretical predictions. The results furthermore suggest that Coulomb crystals in the future may serve as near-ideal media for highfidelity multi-mode quantum information processing and communication purposes, including the generation an…
We compute the photon creation inside a perfectly conducting, three dimensional oscillating cavity, taking the polarization of the electromagnetic field into account. As the boundary conditions for this field are both of Dirichlet and (generalized) Neumann type, we analyze as a preliminary step the dynamical Casimir effect for a scalar field satisfying generalized Neumann boundary conditions. We show that particle production is enhanced with respect to the case of Dirichlet boundary conditions. Then we consider the transverse electric and transverse magnetic polarizations of the electromagneti…
We analyze nonlinear transverse mode coupling in a Kerr medium placed in an optical cavity and its influence on bistability and different kinds of quantum noise reduction. Even for an input beam that is perfectly matched to a cavity mode, the nonlinear coupling produces an excess noise in the fluctuations of the output beam. Intensity squeezing seems to be particularly robust with respect to mode coupling, while quadrature squeezing is more sensitive. However, it is possible to find a mode the quadrature squeezing of which is not affected by the coupling.
Optical cavities in the near-concentric regime have near-degenerate transverse modes; the tight focusing transverse modes in this regime enable strong coupling with atoms. These features provide an interesting platform to explore multi-mode interaction between atoms and light. Here, we use a spatial light modulator (SLM) to shape the phase of an incoming light beam to match several Laguerre-Gaussian (LG) modes of a near-concentric optical cavity. We demonstrate coupling efficiency close to the theoretical prediction for single LG modes and well-defined combinations of them, limited mainly by i…
Optomechanical devices in which a flexible SiN membrane is placed inside an optical cavity allow for very high finesse and mechanical quality factor in a single device. They also provide fundamentally new functionality: the cavity detuning can be a quadratic function of membrane position. This enables a measurement of "position squared" ($x^2$) and in principle a QND phonon number readout of the membrane. However, the readout achieved using a single transverse cavity mode is not sensitive enough to observe quantum jumps between phonon Fock states. Here we demonstrate an $x^2$-sensitivity that …
We report the confinement of large clouds of ultra-cold 85-Rb atoms in a standing-wave dipole trap formed by the two counter-propagating modes of a high-Q ring-cavity. Studying the properties of this trap we demonstrate loading of higher-order transverse cavity modes and excite recoil-induced resonances.
Quantum storage and retrieval of light in ion Coulomb crystals using cavity electromagnetically induced transparency is investigated theoretically. It is found that, when both the control and probe fields are coupled to the same cavity mode, their transverse mode profile affects the quantum memory efficiency in a non-trivial way. Under such conditions the control field parameters and crystal dimensions that maximize the memory efficiency are calculated.
While relatively easy to engineer, static transverse coupling between a qubit and a cavity mode satisfies the criteria for a quantum non-demolition (QND) measurement only if the coupling between the qubit and cavity is much less than their mutual detuning. This can put significant limits on the speed of the measurement, requiring trade-offs in the circuit design between coupling, detuning, and decoherence introduced by the cavity mode. Here, we study a circuit in which the qubit-cavity and the cavity-feedline coupling can be turned on and off, which helps to isolate the qubit. We do not rely o…
We investigate electromagnetically induced transparencies with two transverse Bose-Einstein condensates in four-mirror optical cavity, driven by a strong pump laser and a weak probe laser. The cavity mode, after getting split from beam splitter, interacts with two independent Bose-Einstein Condensates transversely trapped in the arms of the cavity along $x$-axis and $y$-axis. The interaction of intra-cavity optical mode excites momentum side modes in Bose-Einstein Condensates, which then mimic as two atomic mirrors coupled through cavity field. We show that the probe field photons transition t…
Phase Diagram and dynamical phases of self organization of a Bose-Einstein condensate in a transversely pumped red-detuned cavity
研究了玻色-爱因斯坦凝聚体在横向泵浦红移腔中的相图和动态相，揭示了自组织现象中的稳定性、混沌轨迹和时空模式形成机制。
We demonstrate the trajectory measurement of the single neutral atoms deterministically using a high-finesse optical micro-cavity. Single atom strongly couples to the high-order transverse vacuum TEM_{10} mode, instead of the usual TEM_{00} mode, and the parameter of the system is (g_{10},κ,γ)=2π\times (20.5,2.6,2.6)MHz. The atoms simply fall down freely from the magneto-optic trap into the cavity modes and the trajectories of the single atoms are linear. The transmission spectrums of atoms passing through the TEM10 mode are detected by a single photon counting modules and well fitted. Thanks …
In a series of articles we studied the quantum properties of a degenerate optical parametric oscillator tuned to the first family of transverse modes at the subharmonic. We found that, for a cavity having rotational symmetry respect to the optical axis, a TEM$_{10}$ mode with an arbitrary orientation in the transverse plane is emitted above threshold. We proved then that quantum noise induces a random rotation of this bright TEM$_{10}$ mode in the transverse plane, while the mode orthogonal to it, the so-called dark mode, has perfect quadrature squeezing irrespective of the distance to thresho…
We introduce a method for the conditional generation of nonclassical states of light in a cavity. We consider two-level atoms traveling along the transverse direction to the cavity axis and show that by conditioning on one of the output measurements nonclassical field states are generated. The two-level atoms are prepared in the ground state and we conditioned on the events in which they are also detected in the ground state. Nonclassical properties of the cavity mode are identified and characterized. This includes: quadrature squeezing, sub-Poissonian photon-number distributions, and negative…
The strong light-matter optomechanical coupling offered by Coherent Scattering (CS) set-ups have allowed the experimental realisation of quantum ground state cavity cooling of the axial motion of a levitated nanoparticle [U. Delić et al., Science 367, 892 (2020)]. An appealing milestone is now quantum 2D cooling of the full in-plane motion, in any direction in the transverse plane. By a simple adjustment of the trap polarisation, one obtains two nearly equivalent modes, with similar frequencies $ω_{x}\simω_{y}$ and optomechanical couplings $g_{x}\simeq g_{y}$ -- in this experimental configurat…
Quasi-transverse-electric and -transverse-magnetic fundamental whispering gallery modes in a polymer-coated silica microtoroid are theoretically investigated and demonstrated to possess very high-quality factors. The existence of a nanometer-thickness layer not only evidently reduces the cavity mode volume but also draws the maximal electric field's position of the mode to the outside of the silica toroid, where single quantum dots or nanocrystals are located. Both effects result in a strongly enhanced coherent interaction between a single dipole (for example, a single defect center in a diamo…
We evaluate the squeezing of a probe beam with a transverse Gaussian profile interacting with an ensemble of two-level atoms in a cavity. We use the linear input-output formalism where the effect of atoms is described by susceptibility and noise functions. The transverse structure is accounted for by averaging atomic functions over the intensity profile. The results of the plane-wave and Gaussian-wave theories are compared. When large squeezing is predicted we find the prediction of the plane-wave model not to be reliable outside the Kerr domain. We give an estimate of the squeezing degradatio…
Imaging transverse modes in a GHz surface acoustic wave cavity
本文提出一种基于光纤的扫描迈克尔逊干涉仪，结合外差电路，实现对 GHz 表面声波腔中横向模式的空间分辨成像，揭示了频率重叠的横向模式及其叠加现象。
A single atom strongly coupled to a cavity mode is stored by three-dimensional confinement in blue-detuned cavity modes of different longitudinal and transverse order. The vanishing light intensity at the trap center reduces the light shift of all atomic energy levels. This is exploited to detect a single atom by means of a dispersive measurement with 95% confidence in 0.010 ms, limited by the photon-detection efficiency. As the atom switches resonant cavity transmission into cavity reflection, the atom can be detected while scattering about one photon.
We study the nonequilibrium quantum phase transition of an Ising chain in a dissipative cavity driven by an external transverse light field. When driving and dissipation are in balance, the system can reach a nonequilibrium steady state which undergoes a super-radiant phase transition as the driving strength increases. Interestingly, the super-radiant field changes the effective bias of the Ising chain in return and drives its own transition between the ferromagnetic and paramagnetic phase. We study the rich physics in this system with sophisticated behavior, and investigate important issues i…
We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beamsplitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such as low power beamsplitters ($<100 \mathrm{μW}$), large momentum transfer beamsplitters with modest power, or new self-aligned interferometer geometries utilizing the transverse modes of the optical cavity. As a first demonstration, we obtain Ramsey-Raman fringes with $>75\%$ contrast and measure the acceleration due to gravity, $\mathit{g}$, t…
A microfabricated Fabry-Perot optical resonator has been used for atom detection and photon production with less than 1 atom on average in the cavity mode. Our cavity design combines the intrinsic scalability of microfabrication processes with direct coupling of the cavity field to single-mode optical waveguides or fibers. The presence of the atom is seen through changes in both the intensity and the noise characteristics of probe light reflected from the cavity input mirror. An excitation laser passing transversely through the cavity triggers photon emission into the cavity mode and hence int…
We study light induced spatial crystallization of ultracold quantum particles confined along the axis of a high-$Q$ linear cavity via a transverse multicolor pump using numerical simulations. Whenever a pump frequency is tuned close to resonance with a longitudinal cavity mode, the dynamics favors bistable spatial particle ordering into a Bragg grating at a wavelength distance. Simultaneous pumping at several resonant frequencies fosters competition between the different spatial lattice orders, exhibiting complex nonlinear field dynamics involving several metastable atom-field states. For few …
It has been shown that there are not only transverse but also longitudinal couplings between microwave fields and a superconducting qubit with broken inversion symmetry of the potential energy. Using multiphoton processes induced by longitudinal coupling fields and frequency matching conditions, we design a universal algorithm to produce arbitrary superpositions of two-mode photon states of microwave fields in two separated transmission line resonators, which are coupled to a superconducting qubit. Based on our algorithm, we analyze the generation of evenly-populated states and NOON states. Co…
Raman-phonon-polariton condensation in a transversely pumped cavity
本文提出利用横向泵浦拉曼方案实现可调声子-光子耦合的声子极化激元凝聚，并通过Floquet稳定性分析给出超辐射态和激光态的相图，为工程电子关联态提供新工具。
The interaction between dielectric particles and a laser-driven optical cavity gives rise to both conservative and dissipative dynamics, which can be used to levitate, trap and cool nanoparticles. We analytically and numerically study a two-mode setup in which the optical potentials along the cavity axis cancel, so that the resulting dynamics is almost purely dissipative. For appropriate detunings of the laser-drives, this dissipative optomechanical dynamics can be used to sort particles according to their size, to rectify their velocities and to enhance transverse cooling.
We consider an ensemble of ultracold bosonic atoms within a near-planar cavity, driven by a far detuned laser whose phase is modulated at a frequency comparable to the transverse cavity mode spacing. We show that a strong, dispersive atom-photon coupling can be reached for many transverse cavity modes at once. The resulting Floquet polaritons involve a superposition of a set of cavity modes with a density excitation of the atomic cloud. The mutual interactions between these modes lead to distinct avoided crossings between the polaritons. Increasing the laser drive intensity, a low-lying multim…
Optically accessible high-finesse millimeter-wave resonator for cavity quantum electrodynamics with atom arrays
本文提出一种光学可及的高精细度毫米波法布里-珀罗腔，通过建模傍轴后修正规避近共焦几何引起的横模简并损耗，在1 K下实现精细度5.8×10^7，为囚禁原子阵列的强耦合腔QED实验铺平道路。
Atoms in transversely pumped optical cavities "self-organize" by forming a density wave and emitting superradiantly into the cavity mode(s). For a single-mode cavity, the properties of this self-organization transition are well characterized both theoretically and experimentally. Here, we explore the self-organization of a Bose-Einstein condensate in the presence of two cavity modes---a system that was recently experimentally realized [Leonard \emph{et al.}, \emph{Nature} {\bf 543}, 87 (2017)]. We argue that this system can exhibit a "vestigially ordered" phase in which neither cavity mode exh…
Cavity-optomechanics, a rapidly developing area of research, has made a remarkable progress. A stunning manifestation of optomechanical phenomena is in exploiting the mechanical effects of light to couple the optical degree of freedom with mechanical degree of freedom. In this report, we investigate the controlled bistable dynamics of such hybrid optomechanical system composed of cigar-shaped Bose-Einstein condensate (BEC) trapped inside high-finesse optical cavity with one moving-end mirror and is driven by a single mode optical field. The numerical results provide evidence for controlled opt…
It is commonly thought that thermal photons with transverse electric polarization cannot exist in a planar metallic cavity whose size $a$ is smaller than the thermal wavelength $λ_T$, due to absence of modes with $λ< 2a$. Computations based on a realistic model of the mirrors contradict this expectation, and show that a micron-sized metallic cavity is filled with non-resonant radiation having transverse electric polarization, following a non-Planckian spectrum, whose average density at room temperature is orders of magnitudes larger than that of a black-body. We show that the spectrum of this …
We investigate the controllability of electromagnetically induced transparency (EIT) and Fano resonances in hybrid optomechanical system which is composed of cigar-shaped Bose-Einstein condensate (BEC) trapped inside high-finesse Fabry-Pérot cavity driven by a single mode optical field along the cavity axis and a transverse pump field. Here, transverse optical field is used to control the phenomenon of EIT in the output probe laser field. The output probe laser field can efficiently be amplified or attenuated depending on the strength of transverse optical field. Furthermore, we demonstrate th…
Supersolids are characterized by the counter-intuitive coexistence of superfluid and crystalline order. Here we study a supersolid phase emerging in the steady state of a driven-dissipative system. We consider a transversely pumped Bose-Einstein condensate trapped along the axis of a ring cavity and coherently coupled to a pair of degenerate counter-propagating cavity modes. Above a threshold pump strength the interference of photons scattered into the two cavity modes results in an emergent superradiant lattice, which spontaneously breaks the continuous translational symmetry towards a period…
We investigate the nonlinear light-matter interaction of a Bose-Einstein condensate trapped in an external periodic potential inside an optical cavity which is weakly coupled to vacuum radiation modes and driven by a transverse pump field. Based on a generalized Bose-Hubbard model which incorporates a single cavity mode, we include the collective backaction of the atoms on the cavity light field and determine the nonequilibrium quantum phases within the nonperturbative bosonic dynamical mean-field theory.With the system parameters adapted to recent experiments, we find a quantum phase transiti…
The cavity method is a well established technique for solving classical spin models on sparse random graphs (mean-field models with finite connectivity). Laumann et al. [arXiv:0706.4391] proposed recently an extension of this method to quantum spin-1/2 models in a transverse field, using a discretized Suzuki-Trotter imaginary time formalism. Here we show how to take analytically the continuous imaginary time limit. Our main technical contribution is an explicit procedure to generate the spin trajectories in a path integral representation of the imaginary time dynamics. As a side result we also…
We study an atom-cavity system in which the cavity has several degenerate transverse modes. Mode-resolved cavity transmission spectroscopy reveals well-resolved atom-cavity resonances for several cavity modes, a signature of collective strong coupling for the different modes. Furthermore, the experiment shows that the cavity modes are coupled via the atomic ensemble contained in the cavity. The experimental observations are supported by a detailed theoretical analysis. The work paves the way to the use of interacting degenerate modes in cavity-based quantum information processing, where qubits…
Interfacing solid-state emitters with photonic structures is a key strategy for developing highly efficient photonic quantum technologies. Such structures are often organised into two distinct categories: nanocavities and waveguides. However, any realistic nanocavity structure simultaneously has characteristics of both a cavity and waveguide, which is particularly pronounced when the cavity is constructed using low-reflectivity mirrors in a waveguide structure with good transverse light confinement. In this regime, standard cavity quantum optics theory breaks down, as the waveguide character o…
We propose a novel type of composite light-matter magnetometer based on a transversely driven multi-component Bose-Einstein condensate coupled to two distinct electromagnetic modes of a linear cavity. Above the critical pump strength, the change of the population imbalance of the condensate caused by an external magnetic field entails the change of relative photon number of the two cavity modes. Monitoring the cavity output fields thus allows for nondestructive measurement of the magnetic field in real time. We show that the sensitivity of the proposed magnetometer exhibits Heisenberg-like sca…
4H-SiC microring opto-mechanical oscillator with a self-injection locked pump
首次实现DFB激光器对4H-SiC微环的自注入锁定，在低阈值下观测到谐振光机械振荡，为即插即用孤子微梳及腔光力学发展奠定基础。
We present protocols for creating entangled states of two modes of the electromagnetic field, by using a beam of atoms crossing microwave resonators. The atoms are driven by a transverse, classical field and pump correlated photons into (i) two modes of a cavity and (ii) the modes of two distant cavities. The protocols are based on a stochastic dynamics, characterized by random arrival times of the atoms and by random interaction times between atoms and cavity modes. The resulting effective model yields a master equation, whose steady state is an entangled state of the cavity modes. In this re…
Recent experimental advances in the field of cold-atom cavity QED provide a powerful tool for exploring non-equilibrium correlated quantum phenomena beyond conventional condensed-matter scenarios. We present the dynamical phase diagram of a driven Bose-Einstein condensate coupled with the light field of a cavity, with a transverse driving field red-detuned from atomic resonance. We identify regions in parameter space showing dynamical instabilities in the form of limit cycles, which evolve into chaotic behavior in the strong driving limit. Such limit cycles originate from the interplay between…
We explore the density and spin self-ordering of driven spin-$1/2$ collisionless fermionic atoms coupled to the electromagnetic fields of a ring resonator. The two spin states are two-photon Raman-coupled via a pair of degenerate counterpropagating cavity modes and two transverse pump fields. In this one-dimensional configuration the coupled atom-field system possesses a continuous $U(1)$ translational symmetry and a discrete $\mathbf{Z}_2$ spin inversion symmetry. At half filling for sufficiently strong pump strengths, the combined $U(1)\times \mathbf{Z}_2$ symmetry is spontaneously broken at…
Microwave cavities with high quality factors enable coherent coupling of distant quantum systems. Virtual photons lead to a transverse exchange interaction between qubits, when they are non-resonant with the cavity but resonant with each other. We experimentally probe the inverse scaling of the inter-qubit coupling with the detuning from a cavity mode and its proportionality to the qubit-cavity interaction strength. We demonstrate that the enhanced coupling at higher frequencies is mediated by multiple higher-harmonic cavity modes. Moreover, in the case of resonant qubits, the symmetry propert…
Digital Micromirror Devices (DMD) provide a robust platform with which to implement digital holography, in principle providing the means to rapidly generate propagating transverse electromagnetic fields with arbitrary mode profiles at visible and IR wavelengths. We use a DMD to probe a Fabry-Pérot cavity in single-mode and near-degenerate confocal configurations. Pumping arbitrary modes of the cavity is possible with excellent specificity by virtue of the spatial overlap between the incident light field and the cavity mode.
We determine the quantum ground-state properties of ultracold bosonic atoms interacting with the mode of a high-finesse resonator. The atoms are confined by an external optical lattice, whose period is incommensurate with the cavity mode wave length, and are driven by a transverse laser, which is resonant with the cavity mode. While for pointlike atoms photon scattering into the cavity is suppressed, for sufficiently strong lasers quantum fluctuations can support the build-up of an intracavity field, which in turn amplifies quantum fluctuations. The dynamics is described by a Bose-Hubbard mode…
We propose a scheme to investigate whether non-uniform motion degrades entanglement of a relativistic quantum field that is localised both in space and in time. For a Dirichlet scalar field in a cavity in Minkowski space, in small but freely-adjustable acceleration of finite but arbitrarily long duration, degradation of observable magnitude occurs for massless transverse quanta of optical wavelength at Earth gravity acceleration and for kaon mass quanta already at microgravity acceleration. We outline a space-based experiment for observing the effect and its gravitational counterpart.
Quantum computation and communication protocols require quantum resources which are in the continuous variable regime squeezed and/or quadrature entangled optical modes. To perform more and more complex and robust protocols, one needs sources that can produce in a controlled way highly multimode quantum states of light. One possibility is to mix different single mode quantum resources. Another is to directly use a multimode device, either in the spatial or in the frequency domain. We present here the first experimental demonstration of a device capable of producing simultanuously several squee…
In this paper, we investigate the effect of atomic collisions on the phase transition form the normal to the superradiant phase in a one-dimensional Bose-Einstein condensate (BEC) trapped inside an optical cavity. Specifically, we show that driving the atoms from the side of the cavity leads to the excitation of modes in the edges of the first Brillouin zone of every energy band, which results in the two-mode approximation of the BEC matter field in the limit of weak coupling regime. The nonlinear effect of atom-atom interaction shifts the threshold of the quantum phase transition of the BEC a…
We propose that condensed matter phenomena involving the spontaneous emergence and dynamics of crystal lattices can be realized in the setting of ultracold Bose-condensed atoms coupled to multimode cavities. Previously, it was shown that in the case of a transversely pumped single-mode cavity, the atoms self-organize at either the even or the odd antinodes of the cavity mode, given sufficient pump intensity, and hence spontaneously break a discrete translational symmetry. Here, we demonstrate that in multimode cavities the self-organization brings the additional feature of continuous translati…
Mode mixing and losses in misaligned microcavities
本文研究了横向失准法布里-珀罗腔在球形和高斯镜面下的模式混合与光学损耗，发现球形镜面在简并处存在保护性模式混合，而高斯镜面会导致严重模式畸变和损耗升高，建议设计腔实验时重视镜面轮廓影响。
Fluctuation-Induced Bistability of Fermionic Atoms Coupled to a Dissipative Cavity
本文研究了费米子原子耦合到耗散腔的稳态相图，发现考虑涨落后系统在泵浦强度临界值发生自组织相变，且在更大泵浦强度下出现涨落诱导的双稳态，该现象无法被平均场方法捕捉。
Demonstration of strong coupling of a subradiant atom array to a cavity vacuum
本研究实验证明，在未驱动高精细度腔中，冷原子阵列通过相消干涉实现亚辐射，强集体耦合导致真空拉比劈裂及显著偏振旋转，展示了强耦合真空场的独特效应。
We demonstrate how the term describing interaction between a single two-level atom and two cavity field modes may attain a Rashba form. As an outcome, cavity QED provides a testbed for studies of phenomena reminiscent of the spin-orbit induced anomalous Hall effect. The effective magnetic field, deriving from the non-Abelian gauge potentials rendered by the Rashba coupling, induces a transverse force acting on the phase space distributions. Thereby, the phase space distributions build up a transverse motion manifesting itself in spiral trajectories, rather than circular ones obtained for a zer…
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