Photon-number Squeezing Research Articles

Photon-number squeezing in nano- and microlasers

Based on theoretical predictions on the appearance of antibunching before the laser threshold at the nano- and microscale, we analyze the amount of photon-number squeezing naturally produced in the laser emission. Up to 3 dB photon number noise reduction is obtained in comparison with the coherent emission, with output power in the range of pW and with negligible effects due to pump fluctuations. The scheme requires a moderately high Q cavity and holds promise for the construction of a simple and effective photon-number squeezed source.

Generalized photon-subtracted squeezed vacuum states

We construct a generalized version of the photon-subtracted squeezed vacuum states (PSSVS), which can be utilized to construct the same for nonlinear, deformed and any usual quantum mechanical models beyond the harmonic oscillator. We apply our general framework to trigonometric Pöschl–Teller potential and show that our method works accurately and produces a proper nonclassical state. We analyze the nonclassicality of the state using three different approaches, namely, quadrature squeezing, photon number squeezing and Wigner function and indicate how the standard definitions of those three techniques can be generalized and utilized to examine the nonclassicality of any generalized quantum optical states including the PSSVS. We observe that the generalized PSSVS are always more nonclassical than those arising from the harmonic oscillator. Moreover, within some quantification schemes, we find that the nonclassicality of the PSSVS increases almost proportionally with the number of photons subtracted from the generalized squeezed vacuum state. Thus, generalized PSSVS may provide an additional freedom with which one can regulate the nonclassicality and obtain an appropriate nonclassical state as per requirement.

Dynamics of entanglement and non-classicality features of a single-mode nonlinear Jaynes–Cummings model

Abstract In this paper, we discuss a model of a nonlinear interaction between a λ-type four-level atom interacting with a cavity field. The analytical solution of the system under particular conditions has been obtained. Numerical treatments have been discussed and new features of the entanglement degree are obtained using entropy and Mandel Q-parameter. Moreover, we evaluate a few of their non-classical properties such as momentum increment, momentum diffusion, mean photon number and normal squeezing. The Kerr medium impact has been discussed through different phenomena. It is shown that Kerr-like medium parameter can be used as a controller parameter of the system dynamics.

Superposed Output Coherent and Squeezed Laser Light Beams

The aim of this paper is to analyze the squeezing and statistical properties of superposed output coherent and squeezed laser light beams. In order to carry out the analysis, we have obtained the superposition density operator along with the Q functions, we have calculated the mean photon number, the photon number variance and the quadrature variances for the superposed output light beams. It has been found that the mean photon number and quadrature variances of the superposed output light beams are the sum of the mean photon number and quadrature variances of the separate light beams, respectively. In addition, the mean photon number and quadrature squeezing of the superposed output light beams increase with linear gain coefficient. Keywords: Superposed, Squeezing, Density operator, Coherent light, Photon statistics. DOI : 10.7176/APTA/77-03 Publication date :May 31 st 2019

Overcoming inefficient detection in sub-shot-noise absorption measurement and imaging.

Photon-number squeezing and correlations enable measurement of absorption with an accuracy exceeding that of the shot-noise limit. However, sub-shot noise imaging and sensing based on these methods require high detection efficiency, which can be a serious obstacle if measurements are carried out in "difficult" spectral ranges. We show that this problem can be overcome through the phase-sensitive amplification before detection. Here we propose an experimental scheme of sub-shot-noise imaging with tolerance to detection losses.

Quantum dynamics of a BEC interacting with a single-mode quantized field under the influence of a dissipation process: thermal and squeezed vacuum reservoirs

In this paper we consider a system consisting of a number of two-level atoms in a Bose–Einstein condensate (BEC) and a single-mode quantized field, which interact with each other in the presence of two different damping sources, i.e. cavity and atomic reservoirs. The reservoirs which we consider here are thermal and squeezed vacuum ones corresponding to field and atom modes. Strictly speaking, by considering both types of reservoirs for each of the atom and field modes, we investigate the quantum dynamics of the interacting bosons in the system. Then, via solving the quantum Langevin equations for such a dissipative BEC system, we obtain analytical expressions for the time dependence of atomic population inversion, mean atom as well as photon number and quadrature squeezing in the field and atom modes. Our investigations demonstrate that for modeling the real physical systems, considering the dissipation effects is essential. Also, numerical calculations which are presented show that the atomic population inversion, the mean number of atoms in the BEC and the photons in the cavity possess damped oscillatory behavior due to the presence of reservoirs. In addition, non-classical squeezing effects in the field quadrature can be observed especially when squeezed vacuum reservoirs are taken into account. As an outstanding property of this model, we may refer to the fact that one can extract the atom–field coupling constant from the frequency of oscillations in the mentioned quantities such as atomic population inversion.

Dynamics of Entropy and Nonclassicality Features of the Interaction between a ⋄-type Four-Level Atom and a Single-Mode Field in the Presence of Intensity-Dependent Coupling and Kerr Nonlinearity

The interaction between a ⋄-type four-level atom and a single-mode field in the presence of Kerr medium with intensity-dependent coupling involving multi-photon processes has been studied. Using the generalized (nonlinear) Jaynes—Cummings model, the exact analytical solution of the wave function for the considered system under particular condition, has been obtained when the atom is initially excited to the topmost level and the field is in a coherent state. Some physical properties of the atom-field entangled state such as linear entropy showing the entanglement degree, Mandel parameter, mean photon number and normal squeezing of the resultant state have been calculated. The effects of Kerr medium, detuning and the intensity-dependent coupling on the temporal behavior of the latter mentioned nonclassical properties have been investigated. It is shown that by appropriately choosing the evolved parameters in the interaction process, each of the above nonclassicality features, which are of special interest in quantum optics as well as quantum information processing, can be revealed.

Photon number squeezing in repeated parametric downconversion with ancillary photon-number measurements.

We present a realistic numerical simulation of a source of number-squeezed photon states employing a cavity-based parametric downconversion (PDC) process. A cavity containing the PDC medium is pumped repeatedly. The cavity recycles only one of the PDC output modes, allowing it to be amplified with each subsequent pump pulse. A photon number resolved (PNR) measurement is made on the other PDC output mode following each pump pulse. Once the PNR measurements indicate that the target number of photons has accumulated in the cavity, the pumping is stopped and the resulting photon state is released. The photon number uncertainty in the resulting state is ~3 dB below that of a mean-equivalent coherent state and furthermore the probability of generating the target photon number is similarly increased.

Photon-number squeezing with a noisy femtosecond fiber laser amplifier source using a collinear balanced detection technique

We experimentally demonstrate photon-number squeezing at 1.55 μm using a noisy erbium-doped fiber amplifier (EDFA). We employ a collinear balanced detection (CBD) technique, where the intensity noise at a specific radio frequency is canceled between two pulse trains. In spite of substantially large excess noise (>10 dB) in an EDFA due to amplified spontaneous emission, we successfully cancel the intensity noise and achieve a shot noise limit at a specific radio frequency with the CBD technique. We exploit two sets of fiber polarization interferometers to generate squeezed light and observe a maximal photon-number squeezing of -2.6 dB.

Toward Global Quantum Communication: Beam Wandering Preserves Nonclassicality

Tap-proof long-distance quantum communication requires a deep understanding of the strong losses in transmission channels. Here we provide a rigorous treatment of the effects of beam wandering, one of the leading disturbances in atmospheric channels, on the quantum properties of light. From first principles we derive the probability distribution of the beam transmissivity, with the aim to completely characterize the quantum state of light. It turns out that beam wandering may preserve nonclassical effects, such as entanglement, quadrature and photon number squeezing, much better than a standard attenuating channel of the same losses.

Controllable nonlinear effects in an optomechanical resonator containing a quantum well

We study nonlinear effects in an optomechanical system containing a quantum well. The nonlinearity due to the optomechanical coupling leads to a bistable behavior in the mean intracavity photon number and substantial squeezing in the transmitted field. We show that the optical bistability and the degree of squeezing can be controlled by tuning the power and frequency of the pump laser. The transmitted field intensity spectrum consists of six distinct peaks corresponding to optomechanical, polariton, and hybrid resonances. Interestingly, even though the quantum well and the mechanical modes are not directly coupled, their interaction with the common quantized cavity mode results in appearance of hybrid resonances.

Single-photon generation by correlated loss in a three-core optical fiber

We demonstrate that by an asymmetric coupling of two nonlinear waveguiding cores to the third strongly absorptive core, it is possible to realize single-photon generation on demand from an input coherent state. This three-core fiber setup can also be implemented for achieving strong photon-number squeezing even for large losses in side cores.

Phase properties of odd and even circular states

Phase properties of the even and odd circular states are studied within the Hermitian phase formalism of Pegg and Barnett. Exact analytical formulas for the distribution function and the variance of the phase operator are obtained and used to examine whether or not the even and odd circular states exhibit photon-number squeezing and phase squeezing.

Photon-Number Squeezing in Circuit Quantum Electrodynamics

A superconducting single-electron transistor (SSET) coupled to an anharmonic oscillator, e.g., a Josephson junction-L-C circuit, can drive the latter to a nonequilibrium photon-number distribution. By biasing the SSET at the Josephson quasiparticle cycle, cooling of the oscillator as well as a laserlike enhancement of the photon number can be achieved. Here, we show that the cutoff in the quasiparticle tunneling rate due to the superconducting gap, in combination with the anharmonicity of the oscillator, may create strongly squeezed photon-number distributions. For low dissipation in the oscillator, nearly pure Fock states can be produced.

Plasmon enhanced fluorescence microscopy below quantum noise limit with reduced photobleaching effect

We propose a plasmon enhanced fluorescence microscopy technique below the quantum noise limit. This is achieved by exciting fluorescent molecules with photon number squeezed (PNS) light and using nanoparticles as an enhancer for overcoming the low absorption cross section. PNS light has an inherent sub-Poissonian photon distribution for which the variance Δn<⟨n⟩. PNS light has the added advantage of antibunching, which eliminates photobleaching due to higher order photon interactions. We anticipate that single molecule studies will benefit from such a radiation source.

On SU(1,1) intelligent coherent states

Generalized coherent states associated with SU(1,1) Lie algebra are reviewed. A state is called intelligent if it satisfies the strict equality in the Heisenberg uncertainty relation. The eigenvalue problem satisfied by intelligent states (IS) is solved. The IS associated with SU(1,1) Lie algebra are investigated. We have constructed some realizations for our results of IS, and some applications are discussed. Some nonclassical properties such as Glauber second-order correlation function, photon number distribution and squeezing are investigated.

Generation of 1.5 µm Squeezed Vacuum Pulse Using a Sagnac Loop Interferometer

Photon-number squeezing and quadrature squeezing were studied using ultrafast fibre nonlinear optics pumped by 1.5 µm femtosecond laser pulses. To obtain quadrature squeezing using an Erbium doped fibre amplifiers (EDFA) light source, we developed temporal homodyne technology to exclude the excess noise of an EDFA light source. We also performed a quadrature squeezing experiment using an optical parametric oscillator light source in stead of an EDFA light source exhibiting substantially high excess noise. Although the photon-number squeezing of -3dB was obtained from an asymmetric Sagnac fibre loop, the quadrature noise could not decrease to less than the Shot noise level without cooling the fibre, which is presumably due to GAWBS. To suppress guided acoustic wave Brillouin scattering, we refrigerated the fibre loop by liquid nitrogen, and squeezing at -0.7 dB was obtained by cooling the fiber at liquid nitrogen temperature.

Quantum correlated pulse-pair generation during pulse-trapping propagation in optical fibers

We study a different scheme for generating photon number correlation and squeezing for two copropagating pulses, a soliton and a trapped pulse, in an optical fiber. When the center wavelength of a trapped pulse is close to that of a soliton pulse, the two pulses interact with each other through the third-order optical nonlinear process and exchange photons between the two pulses. The soliton pulse exhibits photon number squeezing. When the center wavelengths of the two pulses are sufficiently separated and no photon-number exchange takes place, the strong negative correlation in the photon number between the parts of the trapped pulse and the soliton pulse is formed via cross-phase modulation. By measuring the photon number of the negatively correlated part of the trapped pulse, we can obtain the photon number of the soliton pulse with a variance less than the shot-noise limit.

Photon-number squeezing in a solitonlike Raman Stokes component during propagation of ultrashort pulses in a microstructure fiber

We discuss the characteristics of photon-number squeezing generated in a spectrally filtered Raman Stokes pulse obtained from a nonlinear fiber. The Raman Stokes pulse generated from a microstructure fiber with a femtosecond input laser pulse exhibits far higher photon-number squeezing. We studied the quantum correlation established among the frequency modes in the Raman Stokes pulse by using numerical calculations and experiments. To design an intra-Stokes pulse quantum correlation through the optical nonlinearities of a fiber to obtain higher photon-number squeezing, we shaped the input laser pulse by using a self-learning closed-loop control approach.

High Photon-Number Squeezing in Strong Field Limit

We show that high photon-number squeezing in bright light can begenerated in both lasers and optical bistabilities by theinjections of a squeezed vacuum and a classical field, and thehigh squeezing is maintained for very strong field.