sub-Poissonian Behavior Research Articles

A study of the quasi-probability distributions of the Tavis–Cummings model under different quantum channels

We study the dynamics of the spin and cavity field of the Tavis–Cummings model using quasi-probability distribution functions and the second-order coherence function, respectively. The effects of (non)-Markovian noise are considered. The relationship between the evolution of the cavity photon number and spin excitation under different quantum channels is observed. The equal-time second-order coherence function is used to study the sub-Poissonian behavior of light and is compared with the two-time second-order coherence function in order to highlight the (anti)-bunching properties of the cavity radiation.

Steady state quantum statistics of a hybrid optomechanical-ferromagnet system: photon and magnon blockade

Magnon and photon blockade implementation and manipulation have significant practical applications in quantum information processing and quantum metrology due to their tight relations to single-photon and -magnon source devices. In this paper, we propose an experimentally feasible hybrid scheme for the dynamical description of the tripartite interacting system consisting of magnon and phonon modes with photons in an optomechanical system, from which we aim to explore the quantum statistics, as well as the magnon and photon blockade phenomenon. To achieve the purpose, the dissipative solution of the system is obtained with the help of the Lindblad master equation. Via employing the equal-time second-order correlation function and using the steady state solution of the system, the statistics and blockade effects of magnon and photon are analyzed and also their dependence on the parameters involved in the system are discussed. Utilizing feasible parameters, our simulations illustrate that, sub-Poissonian behavior and therefore, blockade of magnon and photon are simultaneously achieved. More importantly, the mentioned blockade effects can be obtained in a range of parameters (and not with specific) which makes our proposal easy to access, experimentally. Considering the above realizations, the introduced scheme opens up a pathway to design single-magnon and -photon generators, which are of crucial importance in advanced quantum science and technologies.

London-modified coherent states: statistical properties and interaction with a two-level atom

In this paper, we discuss the statistical properties of London-modified coherent states that were introduced in order to build up a resolution of the identity for London coherent states. The resolution to the identity is realized by the application of an operator to the London cohrent states. Next we find the Mandel-Q parameter that shows that there exist sub-Poissonian behaviour for a large interval of amplitudes, look at their behaviour in phase space through the Husimi-Q function and study their interaction with a two-level atom. We show that their oscillating photon distributions are responsible for the ringing revival behaviour shown by the atomic inversion.

Squeezing-enhanced superposition of coherent states and their nonclassical properties

We study the squeezing-enhanced superposition of coherent states, which are generated by operating a squeezing operator with two parameters on the superposition of coherent states with a different relative phase. The aim of this study is to discuss the nonclassical properties of these novel states by their quantum statistical and squeezing properties. The results show that the squeezing parameter r and relative phase θ play key roles in these states. It is clear to see that these new quantum states have stronger squeezing, antibunching effect, sub-Poissonian distributions behavior when compared to the normal squeezing superposition of coherent states.

Evolution of the squeezing-enhanced vacuum state in the amplitude dissipative channel

We study the evolution of the squeezing-enhanced vacuum state (SEVS) in the amplitude dissipative channel by using the two-mode entangled state in the Fock space and Kraus operator. The explicit formulation of the output state is also given. It is found that the output state does not exhibit sub-Poissonian behavior for the nonnegative value of the Mandel’s Q-parameters in a wide range of values of squeezing parameter and dissipation factor. It is interesting to see that second-order correlation function is independent of the dissipation factor. However, the photon-number distribution of the output quantum state shows remarkable oscillations with respect to the dissipation factor. The shape of Wigner function and the degree of squeezing show that the initial SEVS is dissipated by the amplitude dissipative channel.

Fano stability diagram of a symmetric triple quantum dot

The Fano factor stability diagram of a C$_{3v}$ symmetric triangular quantum dot is analysed for increasing electron fillings $N$. At low filling, conventional Poissonian and sub-Poissonian behavior is found. At larger filling, $N\ge 2$, a breaking of the electron-hole symmetry is manifested in super-Poissonian noise with a peculiar bias voltage dependence of the Fano factor at Coulomb and interference blockade. An analysis of the Fano map unravels a nontrivial electron bunching mechanism arising from the presence of degenerate many-body states combined with orbital interference and Coulomb interactions. An expression for the associated dark states is provided for generic $N$.

Coherent States Formalism Applied to the Quantum Well Model

The different nanostructures (quantum dots, wires and wells) have specific properties which differ from those of the corresponding bulk structures. This fact leads to many applications in several branches of physics. In the paper we examine the behavior of a quantum system (a free particle and a quantum free particle gas) trapped inside the infinite quantum well, by using the coherent states formalism. Our approach is based on the fact that the dynamical group associated with the infinite quantum well is SU(1, 1), with the Bargmann index k = 1/2. These coherent states always have the sub-Poissonian behavior. There is a similarity between the energy main quantum number n and the absolute value of the complex variable z which labels the coherent states. This allows us to make a useful approximation in order to calculate the partition function and some thermodynamic characteristics of a canonical non interacting particle gas embedded in the infinite square quantum well.

Reduction of single-photon emission from a single-emitter system by intersystem crossing

We investigate the reduction in the probability of single-photon emission from a single-emitter system caused by intersystem crossing. The physical model is that a single-emitter system with three levels is excited by a square pulse laser, and then a single photon is emitted at a controllable time. We find that the intersystem crossing always reduces the probability of single-photon emission. We obtain quantitative and analytical expressions for the probabilities of zero-, one-, and two-photon emission and Mandel's Q parameter as the function of the intersystem crossing rate under the conditions of finite field strength and finite interaction time with the laser pulse. We discuss the conditions for obtaining the maximal probability of single-photon emission in the presence of intersystem crossing. We find that one can obtain a high probability of single-photon emission from the single-emitter system using square pulse excitation in comparison with continuous wave excitation. Mandel's Q parameter exhibits a transition from a sub-Poissonian behavior to a super-Poissonian behavior due to the influence of intersystem crossing. The calculated Mandel's Q parameter and second-order correlation function of photon emission considering the coherent effect are in better agreement with the experimental data.

COHERENT STATE OF THE EXTENDED SCARF I POTENTIAL AND SOME OF ITS PROPERTIES

Using shape invariance property we construct coherent state for a class of potentials containing Scarf I and its extensions, the solutions of the latter being given in terms of the recently discovered Jacobi-Xl type exceptional polynomials. It is shown that the coherent state possesses the property of resolution of unity and exhibits sub-Poissonian behavior. We then investigate the coherent state of Scarf I potential and its l = 1 extension in some detail to understand the similarities (and differences) between the exceptional orthogonal polynomials and their classical counterparts.

Noise spectrum of a quantum dot–resonator lasing circuit

Single-electron tunneling processes through a double quantum dot can induce a lasing state in an electromagnetic resonator which is coupled coherently to the dot system. Here we study the noise properties of the transport current in the lasing regime, i.e. both the zero-frequency shot noise and the noise spectrum. The former shows a remarkable super-Poissonian behavior when the system approaches the lasing transition, but a sub-Poissonian behavior deep in the lasing state. The noise spectrum contains information about the coherent dynamics of the coupled dot–resonator system. It shows pronounced structures at frequencies matching that of the resonator due to the excitation of photons. For strong interdot Coulomb interaction, we observe asymmetries in the auto-correlation noise spectra of the left and right junctions, which we trace back to asymmetries in the incoherent tunneling channels.

Normal and higher order squeezing in eight-wave mixing process

We investigate theoretically the generation of squeezed states in spontaneous and stimulated eight wave mixing process. It has been found that squeezing occurs in field amplitude, amplitude-squared, amplitude-cubed and fourth power of amplitude states of fundamental mode in the eight wave mixing process. It is found to be dependent on coupling parameter g interaction time t and phase values of the field amplitude. Eight-wave mixing is a process which involves absorption of three pump photons and emission of four probe photons of same frequency and a signal photon of different frequency. It is shown that squeezing is greater in a stimulated interaction than the corresponding squeezing in spontaneous process. It is found that the degree of squeezing depends upon the photon number in first and higher orders. We study the Poissonian behaviour of quantum field in the fundamental mode. It has been found that the field shows sub-Poissonian behaviour in the fundamental mode. The signal to noise ratio has also been studied in different orders and found to be higher in lower orders.

Spin polarizedI-Vcharacteristics and shot noise of Pt atomic wires

We report a first-principles investigation of spin polarized transport properties of Pt atomic chains in contact with two semi-infinite Pt slabs along the (111) direction. Our approach is based on the nonequilibrium Green's function coupled with density functional theory so that the Coulomb interaction is included in the calculation of current and shot noise on the Hartree level. For Pt atomic chains with different numbers of Pt atoms, we calculate the spin polarized I-V curve and shot noise. Our results show that the current increases almost linearly with bias for all Pt atomic structures. The calculated Fano factors are comparable to the recent experimental data and show sub-Poissonian behavior.

SQUEEZING AND PHOTON STATISTICS IN FIVE-WAVE MIXING PROCESS

We investigate theoretically the generation of squeezed states in spontaneous and stimulated five-wave mixing process. It has been found that squeezing occurs in field amplitude, amplitude-squared, amplitude-cubed and fourth-order amplitude states of the fundamental mode in the process. It is found to be dependent on coupling parameter g and phase values of the field amplitude of the fundamental mode. The process involves the absorption of two pump photons each having frequency ω1, emission of two probe photons of same frequency ω2 and a signal photon of frequency ω3. It is shown that squeezing is greater in a stimulated interaction than the corresponding squeezing in the spontaneous process. It is found that the degree of squeezing depends on the photon number in the first and higher orders. We study the statistical behaviour of quantum field in the fundamental mode. It has been found that the field shows sub-Poissonian behavior in this mode.

Phonon distributions of a single-bath mode coupled to a quantum dot

The properties of an unconventional, single-mode phonon bath coupled to a quantum dot are investigated within the rotating wave approximation. The electron current through the dot induces an out of equilibrium bath, with a phonon distribution qualitatively different from the thermal one. In selected transport regimes, such a distribution is characterized by a peculiar selective population of few phonon modes and can exhibit sub-Poissonian behavior. It is shown that such sub-Poissonian behavior is favored by a double occupancy of the dot. The crossover from an unequilibrated to a conventional thermal bath is explored, and the limitations of the rotating wave approximation are discussed.

Squeezing and photon statistical effects in spontaneous and stimulated eight-wave mixing process

Eight-wave mixing is a process which involves absorption of four pump photons and emission of three probe photons of same frequency and a signal photon of different frequency. Squeezing is investigated in the fundamental mode in spontaneous and stimulated eight-wave mixing process using quantum mechanical approach. The presence of squeezing in field amplitude, amplitude-squared and amplitude-cubed in the fundamental mode has been probed. The dependence of squeezing on photon number is established with investigations into degree of squeezing in the first and higher order of field amplitude. The photon statistics of the field in the fundamental mode has also been investigated. It has been found that the field shows sub-Poissonian behaviour in the fundamental mode.

Statistical properties of multiphoton time-dependent three-boson coupled oscillators

We investigate the quantum statistics of three time-dependent coupled oscillators in the presence of multiphoton processes. The system is connected with the two-atom multiphoton Tavis-Cummings model. The solution of the Heisenberg equations of the motion is obtained in a compact form. We assume that the modes are initially prepared in coherent states, and we discuss nonclassical phenomena (squeezing and sub-Poissonian behavior). Further, we examine the joint quasi-distribution functions as well as photon-number distribution and its factorial moments. The system has shown that the nonclassical effect is apparent in compound modes (1,3) and (2,3). Moreover, the superstructure phenomenon is observed when the photon transition is increased.

Photon-number-limiting device for nonclassical light generation

We present a scheme for the realization of a stationary source of nonclassical light, which approximates very well a continuous single-photon source. It consists of a single four-level atom trapped inside a high-finesse optical cavity and Raman coupled to a cavity mode. A selectivity mechanism, based on a field-dependent Stark shift of electronic levels, prevents the occupation of two or more photon states of the quantized mode being excited. The output light of such a source exhibits sub-Poissonian photon-number statistics and antibunching behavior.

Super- and sub-Poissonian photon statistics for single molecule spectroscopy

We investigate the distribution of the number of photons emitted by a single molecule undergoing a spectral diffusion process and interacting with a continuous wave laser field. The spectral diffusion is modeled based on a stochastic approach, in the spirit of the Anderson-Kubo line shape theory. Using a generating function formalism we solve the generalized optical Bloch equations and obtain an exact analytical formula for the line shape and Mandel's Q parameter. The line shape exhibits well-known behaviors, including motional narrowing when the stochastic modulation is fast and power broadening. The Mandel parameter, describing the line shape fluctuations, exhibits a transition from a quantum sub-Poissonian behavior in the fast modulation limit to a classical super-Poissonian behavior found in the slow modulation limit. Our result is applicable for weak and strong laser fields, namely, for arbitrary Rabi frequency. We show how to choose the Rabi frequency in such a way so that the quantum sub-Poissonian nature of the emission process becomes strongest. A lower bound on Q is found and simple limiting behaviors are investigated. A nontrivial behavior is obtained in the intermediate modulation limit, when the time scales for spectral diffusion and the lifetime of the excited state become similar. A comparison is made between our results and previous ones derived, based on the semiclassical generalized Wiener-Khintchine formula.

Nonlinear squeezed states

We consider a nonlinear extension of the single-mode squeezed state and show that it exhibits non-classical sub-Poissonian behaviour based on a nonlinearity function that has been shown to be useful for the description of trapped ions.

Sub-Poissonian shot noise in molecular wires

We investigate the transport behavior of polyene molecules sandwiched between two metallic contacts using the nonequilibrium Green’s function formalism. We calculate both current and noise power as a function of applied voltage and show that they decrease with increasing size of the polyene molecules. We find that even with symmetric connection to metallic contacts, current-versus-voltage curves can be asymmetric for asymmetrically substituted polyenes. Most importantly, we demonstrate a crossover from Poissonian to sub-Poissonian behavior in the shot noise as a function of applied voltage. The algorithm for noise power calculation can be used for designing molecules with low noise.