Generation Of Squeezing Research Articles

Observation of Robust Polarization Squeezing via the Kerr Nonlinearity in an Optical Fiber

AbstractSqueezed light is one of the resources of photonic quantum technology. Among the various nonlinear interactions capable of generating squeezing, the optical Kerr effect is particularly easy‐to‐use. A popular venue is to generate polarization squeezing, which is a special self‐referencing variant of two‐mode squeezing. To date, polarization squeezing generation setups have been very sensitive to fluctuations of external factors and have required careful tuning. In this work, a development of a new all‐fiber setup for polarization squeezing generation is reported. The setup consists of passive elements only and is simple, robust, and stable. More than 5 dB of directly measured squeezing is obtained over long periods of time without any need for adjustments. Thus, the new scheme provides a robust and easy‐to‐set‐up way of obtaining squeezed light applicable to different applications. The impact of pulse duration and pulse power on the degree of squeezing is investigated.

Squeezing level strengthened by a temperature dependent dispersion compensation methodology

Doubly resonant optical parametric oscillator (DR-OPO) is a valuable resource for preparing squeezed state. Temperature dependent dispersion compensation technology has become a popular methodology for high degree squeezing generation with DR-OPO. Nevertheless, details for the realization of temperature dependent DR-OPO have not been demonstrated yet. Here, we have constructed a full experimental layout for charactering the doubly resonant temperatures and verifying the squeezing levels in the phase matching bandwidth of the crystal. Three co-resonance temperatures of 30.74 °C, 42.54 °C and 53.71 °C were directly measured, at which 11.7 dB, 12.3 dB and 11.5 dB squeezing were observed, respectively. The experimental and theoretical results both indicate that the temperature dependent frequency detuning contributes to the discrepancy of the squeezing levels for the three temperature conditions. Careful calibration of the temperature dependent frequency detuning should be tracked to strengthen the squeezing level with DR-OPO.

Multimode quantum squeezing generation via multiple four-wave mixing processes within a single atomic vapor cell

Multimode quantum squeezing plays an essential role in the fields of quantum metrology and quantum information. In this paper, we first construct a three- and four-mode energy-level cascaded four-wave mixing system in a single 85 R b vapor, and then analyze the quantum properties of the produced states, including the covariance matrix and the intensity squeezing with 11 possible Hamiltonians. In addition, the dressing field is applied to modulate the nonlinear susceptibility and the multimode quantum states. Our scheme allows active modulation of the quantum states integrated within the generation step, without the need for any post-operation of the optics. The mode number of the states also can be extended using more pump fields and the dressing effect. Our study provides a promising candidate to generate multimode quantum states and multimode quantum squeezing within a quantum device involved in the construction of practical quantum networks.

Experimental realization of efficient nondegenerate four-wave mixing in cesium atoms.

Nondegenerate four-wave mixing (FWM) in diamond-type atomic systems has important applications in a wide range of fields, including quantum entanglement generation, frequency conversion, and optical information processing. Although the efficient self-seeded nondegenerate FWM with amplified spontaneous emission (ASE) has been realized extensively, the seeded nondegenerate FWM without ASE is inefficient in reported experiments so far. Here we present the experimental realization of the seeded nondegenerate FWM in cesium atoms with a significantly improved efficiency. Specifically, with two pump lasers at 852 and 921 nm and a seed laser at 895 nm, a continuous-wave laser at 876 nm is efficiently generated via FWM in a cesium vapor cell with a power up to 1.2 mW, three orders of magnitude larger than what has been achieved in previous experiments. The improvement of the efficiency benefits from the exact satisfaction of the phase-matching condition realized by an elaborately designed setup. Our results may find applications in the generation of squeezing and entanglement of light via nondegenerate FWM.

Generation and modulation of non-classical light in a strongly coupled photon–emitter system

Non-classical light, especially its single photon and squeezing properties, plays a fundamental role in on-chip quantum networks. The single photon property has been widely studied in photonic cavities including photonic crystals (PhCs), micropillar cavities, nanowires, and plasmonic cavities. However, the generation and modulation of squeezing light in nanophotonic cavities remain to be explored. Here, we theoretically demonstrate a strongly coupled PhC–plasmonic-emitter system enabling non-classical light generation and modulation. The hybridization of a PhC waveguide and an Ag nanoparticle forms a band-edge mode with a narrow linewidth and a strong confined field, which enables strong light–emitter interaction, further resulting in simultaneous generation of squeezing and single photon properties for on-chip applications. Non-classical light emission can be modulated with the detuning between the band-edge mode and the emitter. The emission is efficiently channeled by the PhC waveguide with a high coupling efficiency, accompanying unidirectional transmission under excitation by a circularly polarized emitter. The system provides a candidate for tunable and bifunctional on-chip non-classical light sources at the nanoscale and may offer more possibilities to build versatile quantum networks.

Towards ponderomotive squeezing with SIPS experiment

The core of the experiment presented in this work is a 1-meter scale suspended interferometer with arms cavities, called SIPS (Suspended Interferometer for Ponderomotive Squeezing) and designed to be radiation pressure limited in the frequency band of the gravitational waves ground-based detectors. It will provide both a source of squeezed states by ponderomotive effect and a suitable test bench for the generation of frequency dependent squeezing (FDS) through Einstein Podolsky Rosen (EPR) states filtered in the arms cavities, useful to investigate the possibility to apply these techniques to reduce the quantum noise in the second and/or third generation of interferometric gravitational waves detectors, like Advanced Virgo+ or Einstein Telescope (ET). In this paper we focus, after a summary of the basic principle of the ponderomotive squeezing generation and of the noise that we expect will affect the SIPS sensitivity, on the study and realization of the local and global control system which is necessary to keep the interferometer in its working point.

High-purity pulsed squeezing generation with integrated photonics

Squeezed light has evolved into a powerful tool for quantum technology, ranging from quantum enhanced sensing and quantum state engineering based on partial post-selection techniques. The pulsed generation of squeezed light is of particular interest, as it can provide accurate time stamp and physically defined temporal mode, which are highly preferred in complex communication networks and large-scale information processing. However, the multimode feature of pulsed squeezing in conventional single-pass configuration limits the purity of the output state, negatively impacting its application in quantum technology. In this Letter, we propose a new approach to generate pulsed squeezing with high temporal purity. Pulsed squeezing based on parametric down-conversion in photonic cavities is analyzed. We show that the effective mode number of the output squeezed light approaches unity. Such a high-purity squeezed light can be realized with broad parameters and low pump power, providing a robust approach to generate large-scale quantum resource.

Frequency-dependent squeezing generation with EPR entanglement

The sensitivity of gravitational wave interferometric detectors is ultimately limited by the quantum noise, which arises from the quantum nature of light and it is driven by vacuum fluctuations of the optical field entering from the dark port of the interferometer. One way to improve the sensitivity of gravitational wave interferometers is to inject squeezed vacuum into the dark port. This has been already demonstrated for the main gravitational wave detectors (GEO, Advanced LIGO and Advanced VIRGO). We are studying tricks to produce a “frequency- dependent squeezing”: a standard method is to filter the squeezed optical field with one or more optical cavities (300 m long cavities). An alternative method using a pair of squeezed EPR (Einstein-Podolsky-Rosen) entangled beams to produce frequency-dependent squeezing by a non-degenerate OPO (Optical Parametric Oscillator) will be discussed in this paper. This method promises to achieve a frequency-dependent optimization of the injected squeezed light fields without the need for an external filter cavity.

Study and experiment on the alternative technique of frequency–dependent squeezing generation with EPR entanglement for Virgo

In this paper, we summarize the present state-of-the-art on the proof-of-principle experiment of frequency-dependent squeezing implemented through EPR entanglement for Virgo gravitational-wave detector and we introduce Virgo subsystem proposal for frequency-dependent squeezing, obtained with a compact apparatus and without the costs required by the infrastructure for the filter cavity.

Decoherence assisted spin squeezing generation in superposition of tripartite GHZ and W states

In the present paper, we study spin squeezing under decoherence in the superposition of tripartite maximally entangled GHZ and W states. Here we use amplitude damping, phase damping and depolarisation channel. We have investigated the dynamics of spin squeezing with the interplay of super-position and decoherence parameters with different directions of the mean spin vector. We have found the mixture of GHZ and W states is robust against spin squeezing generation for amplitude damping and phase damping channels for certain directions of the mean spin vector. However, the depolarisation channel performs well for spin squeezing generation and generates permanent spin squeezing in the superposition of GHZ and W states.

Twisting tensor and spin squeezing

A unified tensor description of quadratic spin squeezing interactions is proposed, covering the single- and two-axis twisting as special cases of a general scheme. A closed set of equations of motion of the first moments and variances is derived in Gaussian approximation, and their solutions are discussed from the prospect of fastest squeezing generation. It turns out that the optimum rate of squeezing generation is governed by the difference between the largest and the smallest eigenvalues of the twisting tensor. A cascaded optical interferometer with Kerr nonlinear media is proposed as one of possible realizations of the general scheme.

Two-mode squeezing generation in hybrid chains of superconducting resonators and nitrogen-vacancy-center ensembles

We consider a hybrid quantum system consisting of two independent chains of nearest-neighbor linearly interacting superconducting transmission-line resonators, each of which a nitrogen-vacancy-center ensemble (NVE) is magnetically coupled to. In addition, the first-beginning pair of the resonators is locally driven by a two-mode microwave squeezed bath. We show that in the steady state a series of NVE pairs in the up and down chains is in a two-mode spin squeezed state. In the low excitation limit, collective excitation modes of the up- and down- NVE pairs are in the two-mode squeezed state of the driven field, i.e., realizing a perfect squeezed state replication.

Inducing nonclassical lasing via periodic drivings in circuit quantum electrodynamics.

We show how a pair of superconducting qubits coupled to a microwave cavity mode can be used to engineer a single-atom laser that emits light into a nonclassical state. Our scheme relies on the dressing of the qubit-field coupling by periodic modulations of the qubit energy. In the dressed basis, the radiative decay of the first qubit becomes an effective incoherent pumping mechanism that injects energy into the system, hence turning dissipation to our advantage. A second, auxiliary qubit is used to shape the decay within the cavity, in such a way that lasing occurs in a squeezed basis of the cavity mode. We characterize the system both by mean-field theory and exact calculations. Our work may find applications in the generation of squeezing and entanglement in circuit QED, as well as in the study of dissipative few- and many-body phase transitions.

Generation of squeezed states in coupled cavity chains via dissipation of gap-tunable qubits

A dissipative scheme is proposed to generate single- or two-mode squeezed states in a hybrid quantum system consisting of superconducting resonators and nitrogen-vacancy-center ensembles (NVEs). For the single-mode squeezing generation, we consider an array of linearly coupled superconducting resonators, each of which is magnetically coupled to a NVE. In addition, one of the resonators is coupled to a gap-tunable qubit. It is shown that at steady state all the resonators and NVEs in the array can enter into single-mode squeezed states via dissipation of the qubit. For the two-mode squeezing realization, we consider a pair of superconducting resonator chains, which are coupled to two gap-tunable qubits. We find that at steady state all the resonator pairs in the up and down chains will be steered into two-mode squeezed states via dissipation of the qubits. The present scheme has a remarkable feature: only one or two gap-tunable dissipative qubits are locally involved, and no squeezing resource is required.

Parametric competition in non-autonomous Hamiltonian systems

In this work we use the formalism of chord functions (i.e. characteristic functions) to analytically solve quadratic non-autonomous Hamiltonians coupled to a reservoir composed by an infinity set of oscillators, with Gaussian initial state. We analytically obtain a solution for the characteristic function under dissipation, and therefore for the determinant of the covariance matrix and the von Neumann entropy, where the latter is the physical quantity of interest. We study in details two examples that are known to show dynamical squeezing and instability effects: the inverted harmonic oscillator and an oscillator with time dependent frequency. We show that it will appear in both cases a clear competition between instability and dissipation. If the dissipation is small when compared to the instability, the squeezing generation is dominant and one can see an increasing in the von Neumann entropy. When the dissipation is large enough, the dynamical squeezing generation in one of the quadratures is retained, thence the growth in the von Neumann entropy is contained.

The quadrature squeezing of a mirror in cavity optomechanics coupled with atomic media

Recently [J.Q. Liao, C.K. Law, Phys. Rev. A. 83, 033820 (2011)] theoretically investigated the possibility of generating the quadrature-squeezed states of a moving mirror in a Fabry-Perot cavity. But, the generation of squeezing is limited by the thermal noise of the environment. We propose an approach to lessen such limitations by adding atoms into the cavity. We demonstrate that such a system can lead to a lager squeezing than the case without atoms.

Parametric generation of quadrature squeezing of mirrors in cavity optomechanics

We propose a method to generate quadrature-squeezed states of a moving mirror in a Fabry-Perot cavity. This is achieved by exploiting the fact that when the cavity is driven by an external field with a large detuning, the moving mirror behaves as a parametric oscillator. We show that parametric resonance can be reached approximately by modulating the driving field amplitude at a frequency matching the frequency shift of the mirror. The parametric resonance leads to an efficient generation of squeezing, which is limited by the thermal noise of the environment.

Quantum Squeezing Generation versus Photon Localization in a Disordered Planar Microcavity

We investigate theoretically the nonlinear dynamics induced by an intense pump field in a disordered planar microcavity. Through a self-consistent theory, we show how the generation of quantum optical noise squeezing is affected by the breaking of the in-plane translational invariance and the occurrence of photon localization. We find that the generation of single-mode Kerr squeezing for the ideal planar case can be prevented by disorder as a result of multimode nonlinear coupling, even when the other modes are in the vacuum state. However, the excess noise is a nonmonotonic function of the disorder amplitude. In the strong localization limit, we show that the system becomes protected with respect to this fundamental coupling mechanism and that the ideal quadrature squeezing generation can be obtained.

Generation of continuous variable squeezing and entanglement of trapped ions in time-varying potentials

We investigate the generation of squeezing and entanglement for the motional degrees of freedom of ions in linear traps, confined by time-varying and oscillating potentials, comprised of an DC and an AC component. We show that high degrees of squeezing and entanglement can be obtained by controlling either the DC or the AC trapping component (or both), and by exploiting transient dynamics in regions where the ions' motion is unstable, without any added optical control. Furthermore, we investigate the time-scales over which the potentials should be switched in order for the manipulations to be most effective.

Generation of Squeezing in Higher Order Hermite-Gaussian Modes with an Optical Parametric Amplifier

We demonstrate quantum correlations in the transverse plane of continuous wave light beams by producing −4.0 dB, −2.6 dB and −1.5 dB of squeezing in the TEM00, TEM10 and TEM20 Hermite-Gauss modes with an optical parametric amplifier, respectively. This has potential applications in quantum information networking, enabling parallel quantum information processing. We describe the setup for the generation of squeezing and analyse the effects of various experimental issues such as mode overlap between pump and seed and nonlinear losses.