Thermo Vacuum State Research Articles

Quantum Entanglement via Thermo Excitation on the Thermo Vacuum State

We construct a new state via thermo excitation on the thermo vacuum state. It is interestingly found that partial tracing over thermo-freedom will lead to a negative-binomial state characteristic of l in the a-mode space and annihilating one a-mode photon results in increasing one $\tilde {a}$-mode photon, which exhibits quantum entanglement between system and environment. We employ the summation method within ordered product of operators to proceed our discussion.

Quantum effect of cooling down the environment temperature of mesoscopic LC circuit

ABSTRACTWe examine the quantum effect of cooling down the environment temperature of mesoscopic LC circuit, and find that the ground state of the circuit is no longer in the thermo vacuum state, but in a negative binomial state. We calculate energy of the circuit in this new state, which increases with the cooling of the environment.

Thermo Vacuum State for Describing the Density Operator of Photon-subtracted Squeezed Chaotic Light

For the density operator describing s−photon-subtracted squeezed chaotic light (PSSCL) we search for its thermo vacuum state (a pure state) in the real-fictitious space. We find that it reduces to a thermo vacuum state of squeezed chaotic light when s = 0, and to a thermo vacuum state of the optical negative binomial field when no squeezing. The new thermo vacuum state simplifies calculating photon number average, quantum fluctuation and Mandel’s Q parameter of PSSCL. Using the method of integration within ordered product (IWOP) of operators we also derive the normalization coefficient and explicitly analytical expressions of Wigner function for PSSCL.

Thermo vacuum state for Gaussian-enhanced chaotic light

In nature, there exists superposition of Gaussian light and chaotic light, so we introduce the density operator for describing the Gaussian-enhanced chaotic light (GECL). By virtue of the method of integration within ordered product (IWOP) of operators, we derive its normalization constant. Then, by virtue of the partial trace method, we derive its thermo vacuum state and this may greatly simplify the calculation of photon number average and quantum fluctuation in GECL. It is demonstrated that the second-order degree of coherence of GECL is larger than 2.

Investigating Mesoscopic Non-linear Series Circuit with the Coherent Thermo State Representation

For the first time we considered the quantum effects of mesoscopic non-linear series circuit with the coherent thermo state representation \(\left | \tau \right \rangle \). After introducing the representation \(\left |\tau \right \rangle \), we derived the expression of the density matrix ρ and find that \(\left | \rho \right \rangle _{T} \) presents Gauss type with the representation \(\left | \tau \right \rangle \). In addition, we derived the Wigner function and calculated the quantum fluctuation in the thermo vacuum state |0(β)〉. It is shown that the circuit has the zero current fluctuation because the diode has the reverse saturation current, and the temperature affects the Wigner function of the circuit in thermo vacuum state deeply.

Energy distribution in quantized mesoscopic RLC electric circuit

Quantum information processing experimentally depends on optical-electronic devices. In this paper, we consider quantized mesoscopic RLC (resistance, inductance and capacitance) electric circuit in stable case as a quantum statistical ensemble, and calculate energy distribution (i.e. the energy stored in inductance and capacitance as well as the energy consumed on the resistance). For this aim, we employ the technique of integration within ordered product (IWOP) of operator to derive the thermo-vacuum state for this mesoscopic system, with which ensemble average energy calculation is replaced by evaluating expected value in pure state. This approach is concise and the result we deduced is physically appealling.

Evolution of l-photon excited thermo vacuum state in a single-mode damping channel

In this paper, we investigate how a kind of non-Gaussian states (l-photon excited thermo vacuum state [Formula: see text]) evolves in a single-mode damping channel. We find that it evolves into a Laguerre-polynomial-weighted real–fictitious squeezed thermo vacuum state, which exhibits strong decoherence and its original nonclassicality fades. In particular, when l = 0, in this damping process the thermo squeezing effect decreases while the fictitious-mode vacuum becomes chaotic. In overcoming the difficulty of calculation, we employ the summation method within ordered product of operators, a new generating function formula about two-variable Hermite polynomials is derived.

Expectation Value Theorem for Thermo Vacuum States of Optical Chaotic Field and Negative-Binomial Field

For the density operator (mixed state) describing chaotic light and negative-binomial field there exist the corresponding thermal vacuum state (pure state) in the real-fictitious space. Using the method of integration within ordered product of operators we find the expectation value theorem in these two thermo vacuum states respectively. The thermal average theorem of translation operator is also deduced. Application of the new thermo vacuum state in calculating photon number disturibution and fluctuation and thermal average is presented.

Thermo-vacuum state in a negative binomial optical field and its application

The core of optical field theory at finite temperature is how to introduce the thermo-vacuum state which is the basis of comprehensive investigation of electromagnetic field by virtue of quantum statistic method. Based on the spirit of thermo-field dynamics initiated by Takahashi and Umezawa, we first employ the integration method within the ordered product of operators to search for thermo-vacuum state for the optical negative binomial state (NBS)s=s+1(1-)n|n,+,+,which takes the form of pure negative binomial state. The newly found thermo-vacuum state brings convenience for evaluating the Wigner function of NBS and the fluctuation of photon numbers in NBS.

Evolution of a Thermo Vacuum State in a Single-Mode Amplitude Dissipative Channel

We investigate how an initial thermo vacuum state, in the context of thermo field dynamics, evolves in a single-mode amplitude dissipative channel, and find that in this process the thermo squeezing effect decreases while the fictitious-mode vacuum becomes chaotic.

Generalized Thermo Vacuum State Derived by the Partial Trace Method

By virtue of the technique of integration within an ordered product of operators, we present a new approach for deriving the generalized thermo vacuum state which is simpler in form than that obtained from the Takahashi—Umezawa method. using this new approach, the thermo field dynamics can be developed. Applications of the new state are discussed.