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Quantum Optics|114 Article(s)
Non-classical Properties of Laguerre Polynomial's Photon Added Coherent State
Dao-ming LU
Laguerre polynomial's photon added coherent state is constructed by operation of Laguerre polynomial's photon added operator on coherent state. By the technique of integration within an ordered product of operators, its normalization factor and the calculation expression of 〈ala+m〉 are derived. The influences of the phase angle and the average photon number of coherent state on its non-classical properties are discussed. Numerical results show that, the first-order Laguerre polynomial's photon added coherent state presents squeezing effect, anti-bunching effect, sub-Poissonian statistical property and negativity of Wigner function, and the phase angle of the coherent state has an important influence on its quantum properties. On the other hand, its anti-bunching effect is weakened with the increase of the average photon number of coherent state, and so is the sub-Poissonian distribution property. However, its squeezing property and the negativity of Wigner function are firstly enhanced and then gradually weakened with the increase of the average photon number of coherent state. Laguerre polynomial's photon added coherent state is constructed by operation of Laguerre polynomial's photon added operator on coherent state. By the technique of integration within an ordered product of operators, its normalization factor and the calculation expression of 〈ala+m〉 are derived. The influences of the phase angle and the average photon number of coherent state on its non-classical properties are discussed. Numerical results show that, the first-order Laguerre polynomial's photon added coherent state presents squeezing effect, anti-bunching effect, sub-Poissonian statistical property and negativity of Wigner function, and the phase angle of the coherent state has an important influence on its quantum properties. On the other hand, its anti-bunching effect is weakened with the increase of the average photon number of coherent state, and so is the sub-Poissonian distribution property. However, its squeezing property and the negativity of Wigner function are firstly enhanced and then gradually weakened with the increase of the average photon number of coherent state.
Acta Photonica Sinica
- Publication Date: Jan. 01, 2020
- Vol. 49, Issue 4, 0427001 (2020)
Dependence of Bipartite Entanglement on Qubit-basis in the Amplitude-damping Environment
Xin-wen WANG, Hui-min ZHANG, Ke LIU, and Yan LIU
In order to enhance the intrinsic robustness or prolong the disentangling time of entangled states， the influence of qubi-basis on the robustness of two-qubit entanglement under local amplitude-damping environments is discussed. The decay law and lifetime of entanglement under various qubit-bases are displayed. The optimal qubit-bases in variety of cases are found. When an entangled state is prepared in an optimal qubit-basis， the entanglement decays most slowly and won't disappear in a finite time. The results imply that one could improve the robustness of entangled states by rotating the bases of qubits， which are expected to be helpful for increasing the qualities or efficiencies of entanglement-based quantum protocols. In order to enhance the intrinsic robustness or prolong the disentangling time of entangled states， the influence of qubi-basis on the robustness of two-qubit entanglement under local amplitude-damping environments is discussed. The decay law and lifetime of entanglement under various qubit-bases are displayed. The optimal qubit-bases in variety of cases are found. When an entangled state is prepared in an optimal qubit-basis， the entanglement decays most slowly and won't disappear in a finite time. The results imply that one could improve the robustness of entangled states by rotating the bases of qubits， which are expected to be helpful for increasing the qualities or efficiencies of entanglement-based quantum protocols.
Acta Photonica Sinica
- Publication Date: Oct. 15, 2020
- Vol. 49, Issue 10, 1027002 (2020)
Quantum Theory of Optical Fractional Fourier Transform
Ke ZHANG, Lan-lan LI, Hai-jun YU, Jian-ming DU, and Hong-yi FAN
The aim of this paper is to find out the operator for generating fractional Fourier transform in Hermitian polynomial theory with the operator as the argument， and to incorporate fractional Fourier transform into quantum theory. The role of coordinate-momentum exchanging operator is explored in playing FFrT's addition rule. In the whole derivation the generalized generating function formula of operator Hermitian polynomials and the integration method within ordered product of operators are used. The core of operator Hermite polynomial theory is the operator identity HnQ=:2Qn:， which turns the operator of complex special function into power series in normal ordering， as a result，this greatly simplifies calculations. The aim of this paper is to find out the operator for generating fractional Fourier transform in Hermitian polynomial theory with the operator as the argument， and to incorporate fractional Fourier transform into quantum theory. The role of coordinate-momentum exchanging operator is explored in playing FFrT's addition rule. In the whole derivation the generalized generating function formula of operator Hermitian polynomials and the integration method within ordered product of operators are used. The core of operator Hermite polynomial theory is the operator identity HnQ=:2Qn:， which turns the operator of complex special function into power series in normal ordering， as a result，this greatly simplifies calculations.
Acta Photonica Sinica
- Publication Date: Oct. 15, 2020
- Vol. 49, Issue 10, 1027001 (2020)
Influences of the Ice-water Mixed Clouds on the Performance of Quantum Satellite Communication
NIE Min, REN Jia-ming, YANG Guang, ZHANG Mei-ling, and PEI Chang-xing
According to the spectral distribution function and the extinction factor of the ice crystal and the water droplet in the ice-water mixed clouds, the attenuation relationships between the ratio of ice and water and the channel of the quantum satellite communication were attained. For the bit flipping channels and the depolarizing channels, the equations between the ratio of ice and water and the channel capacity, and the channel average fidelity were established respectively. The effect of the ratio of ice and water in the ice-water mixed clouds on the quantum channel establishing rate was analyzed. The simulation results show that, when the ratio of ice and water in the ice-water mixed clouds is 1∶2 and 1∶9, for the bit flipping channel, the channel capacity is 0.65 and 0.92, and for the depolarizing channel that is 0.59 and 0.95 respectively. When the probability of the source character is 0.9, for the bit flipping channel, the channel average fidelity is 0.60 and 0.83, and for the depolarizing channel that is 0.89 and 0.95 respectively. When the transmission distance is 2 km, the fidelity of the entangled particle pair is 0.8, the quantum channel establishing rate is 7.40Hz and 15.57Hz respectively. Therefore, when the quantum satellite signs are appearing a greater attenuation, in order to improve the reliability of the quantum satellite communication, the parameters should be adjusted adaptively in light of the ratio of ice and water in the ice-water mixed clouds. According to the spectral distribution function and the extinction factor of the ice crystal and the water droplet in the ice-water mixed clouds, the attenuation relationships between the ratio of ice and water and the channel of the quantum satellite communication were attained. For the bit flipping channels and the depolarizing channels, the equations between the ratio of ice and water and the channel capacity, and the channel average fidelity were established respectively. The effect of the ratio of ice and water in the ice-water mixed clouds on the quantum channel establishing rate was analyzed. The simulation results show that, when the ratio of ice and water in the ice-water mixed clouds is 1∶2 and 1∶9, for the bit flipping channel, the channel capacity is 0.65 and 0.92, and for the depolarizing channel that is 0.59 and 0.95 respectively. When the probability of the source character is 0.9, for the bit flipping channel, the channel average fidelity is 0.60 and 0.83, and for the depolarizing channel that is 0.89 and 0.95 respectively. When the transmission distance is 2 km, the fidelity of the entangled particle pair is 0.8, the quantum channel establishing rate is 7.40Hz and 15.57Hz respectively. Therefore, when the quantum satellite signs are appearing a greater attenuation, in order to improve the reliability of the quantum satellite communication, the parameters should be adjusted adaptively in light of the ratio of ice and water in the ice-water mixed clouds.
Acta Photonica Sinica
- Publication Date: Jan. 01, 2016
- Vol. 45, Issue 9, 927004 (2016)
Quantum Properties of Double Two-level Atoms Interacting with Pólya State Light under Intensity Dependent Coupling Condition
LI Bin, Sachuerfu, and GUO Cai-li
The linear entropy and atomic inversion and entropy squeezing in a system of double two-level atoms interacting with a single mode light field at Pólya state under intensity dependent coupling condition were studied by means of full quantum theory. The influences of the initial state of atoms and different parameters of the light field and parameters of Lamb-Dicke on the linear entropy, atomic inversion and entropy squeezing were discussed. The results show that, when the atom in different initial states, the quantum properties of the system are completely different. The period of oscillation increases with the light field parameter of p. Increasing the value of the light field parameter r, which causes the amplitude change and the collapse-recovery phenomenon and the entropy squeezing are destroyed. The linear entropy and atomic inversion and entropy squeezing in a system of double two-level atoms interacting with a single mode light field at Pólya state under intensity dependent coupling condition were studied by means of full quantum theory. The influences of the initial state of atoms and different parameters of the light field and parameters of Lamb-Dicke on the linear entropy, atomic inversion and entropy squeezing were discussed. The results show that, when the atom in different initial states, the quantum properties of the system are completely different. The period of oscillation increases with the light field parameter of p. Increasing the value of the light field parameter r, which causes the amplitude change and the collapse-recovery phenomenon and the entropy squeezing are destroyed.
Acta Photonica Sinica
- Publication Date: Jan. 01, 2016
- Vol. 45, Issue 9, 927003 (2016)
Research on the Lasing Performance of a Quantum Dot-Microcavity System with Pure Dephasing
CHEN Xing, QIN Li-guo, and WANG Qin
By employing the Master Equation theory, the lasing properties of the quantum dot-microcavity coupling system were studied. For different types of coupling systems, i.e., “good system” and “more realistic system”, their lasing phenomenon under external pump field were investigated individually. Moreover, the influence of the detuning and the pure dephasing on internal characteristics of the coupling system, such as its second-order correlation function at zero time delay or the number of photons in cavities was analyzed. The numerical simulations show that, for a “good system”, when the detuning between a quantum dot and a cavity is not very large, the certain pure dephasing can improve the lasing properties of the coupled system; for a “more realistic system”, due to the difficulty of photon gathering in a cavity under off-resonant conditions, it is very hard to observe the lasing phenomenon. However, the pure dephasing will still play an important role on modulating the light field and the photon numbers in the cavity. These results may play positive effects on some research either on lasing with the single quantum dot, or modulating the interaction between light and matter etc. By employing the Master Equation theory, the lasing properties of the quantum dot-microcavity coupling system were studied. For different types of coupling systems, i.e., “good system” and “more realistic system”, their lasing phenomenon under external pump field were investigated individually. Moreover, the influence of the detuning and the pure dephasing on internal characteristics of the coupling system, such as its second-order correlation function at zero time delay or the number of photons in cavities was analyzed. The numerical simulations show that, for a “good system”, when the detuning between a quantum dot and a cavity is not very large, the certain pure dephasing can improve the lasing properties of the coupled system; for a “more realistic system”, due to the difficulty of photon gathering in a cavity under off-resonant conditions, it is very hard to observe the lasing phenomenon. However, the pure dephasing will still play an important role on modulating the light field and the photon numbers in the cavity. These results may play positive effects on some research either on lasing with the single quantum dot, or modulating the interaction between light and matter etc.
Acta Photonica Sinica
- Publication Date: Jan. 01, 2016
- Vol. 45, Issue 9, 927002 (2016)
Majorana Fermions Detection Based on the Coherent Optical Spectrum of a Quantum Dot
CHEN Hua-jun, and FANG Xian-wen
The existence of Majorana fermions in hybrid semiconductor/superconductor heterostructures was studied, and an all-optical method to probe the Majorana fermions by using coherent optical spectra was presented. A strong pump laser and a weak probe laser were acted on semiconductor quantum dot, and the coherent optical spectra were derived by the Hamiltonian of system. The numerical results indicate that the coherent optical spectra present a distinct signature of the coupling between the semiconductor quantum dot and the Majorana fermions in the optical detection method. The characteristic of non-contact between the semiconductor quantum dot and the Majorana fermions can make the detection process avoid introducing noises. The coupling strength between the semiconductor quantum dot and the Majorana fermions is proportional to the distance of two the peaks in the probe absorption spectrum, so that the coupling strength can be obtained by measuring the distance of two the peaks, which presents a straight forward means to determine the coupling strength.MOURIK V, ZUO K, FROLOV S M, et al. Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices［J］. Science, 2012, 336(6084): 1003-1007. The existence of Majorana fermions in hybrid semiconductor/superconductor heterostructures was studied, and an all-optical method to probe the Majorana fermions by using coherent optical spectra was presented. A strong pump laser and a weak probe laser were acted on semiconductor quantum dot, and the coherent optical spectra were derived by the Hamiltonian of system. The numerical results indicate that the coherent optical spectra present a distinct signature of the coupling between the semiconductor quantum dot and the Majorana fermions in the optical detection method. The characteristic of non-contact between the semiconductor quantum dot and the Majorana fermions can make the detection process avoid introducing noises. The coupling strength between the semiconductor quantum dot and the Majorana fermions is proportional to the distance of two the peaks in the probe absorption spectrum, so that the coupling strength can be obtained by measuring the distance of two the peaks, which presents a straight forward means to determine the coupling strength.MOURIK V, ZUO K, FROLOV S M, et al. Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices［J］. Science, 2012, 336(6084): 1003-1007.
Acta Photonica Sinica
- Publication Date: Jan. 01, 2016
- Vol. 45, Issue 9, 927001 (2016)
Decoherence of Weak Coherent State in the Diffusion Process
QIU Chang-dong, and LU Dao-ming
The quantum properties of weak cohetent state in terms of squeezing effect and antibunching effect were investigated in the diffusion. Master equation of density operator in the diffusion process can be concisely solved by virtue of thermo-entangled state representation and the technique of integration within an ordered product of operators, which contains normal ordering, antinormal ordering and Weyl ordering. The solution of master equation of density operator in diffusion process was given by Kraus operator. The evolution formula of the field density operator which is in weak coherent state initially was get . Its squeezing effect and antibunching are investigated by the numerical method. The effect of decoherence on its nonclassical property is discussed. Numerical results show that compression depth is weakened and the compression range decreases with diffusion time increasing. On the other hand, the light field displays antibunching effect in the early diffusion. When the diffusion time is greater than a certain value, its antibunching effect disappears. The quantum properties of weak cohetent state in terms of squeezing effect and antibunching effect were investigated in the diffusion. Master equation of density operator in the diffusion process can be concisely solved by virtue of thermo-entangled state representation and the technique of integration within an ordered product of operators, which contains normal ordering, antinormal ordering and Weyl ordering. The solution of master equation of density operator in diffusion process was given by Kraus operator. The evolution formula of the field density operator which is in weak coherent state initially was get . Its squeezing effect and antibunching are investigated by the numerical method. The effect of decoherence on its nonclassical property is discussed. Numerical results show that compression depth is weakened and the compression range decreases with diffusion time increasing. On the other hand, the light field displays antibunching effect in the early diffusion. When the diffusion time is greater than a certain value, its antibunching effect disappears.
Acta Photonica Sinica
- Publication Date: Jan. 01, 2015
- Vol. 44, Issue 2, 227002 (2015)
The Influence of Faraday Mirror′s Imperfection in Continuous Variable Quantum Key Distribution System
YANG Rong-huan, and HE Guang-qiang
The influence of imperfect Faraday mirror on secret key rate of continuous variable quantum key distribution system in reverse reconciliation is considered with theoretical analysis and numerical simulation. It takes entanglement based scheme. It′s found that Faraday mirror′s imperfection reduces the secret key rate and transmission distance of system. The impact increases if the imperfection turns more serious. Besides it finds using great modulation variance can reduce the impact of Faraday mirror significantly. The influence of imperfect Faraday mirror on secret key rate of continuous variable quantum key distribution system in reverse reconciliation is considered with theoretical analysis and numerical simulation. It takes entanglement based scheme. It′s found that Faraday mirror′s imperfection reduces the secret key rate and transmission distance of system. The impact increases if the imperfection turns more serious. Besides it finds using great modulation variance can reduce the impact of Faraday mirror significantly.
Acta Photonica Sinica
- Publication Date: Jan. 01, 2015
- Vol. 44, Issue 2, 227001 (2015)
Non-classical Properties of Photon Distribution of Entangled Double Atoms Interacting with Coherent Field
ZHAO Jia-qiang
The time evolution properties of photon distribution in the interaction of entangled double atoms and coherent field are studied by means of numerical calculation.The results show that the coherent field which has not photon anti-bunching and photon sub-Poisson distribution can gain these non-classical properties through the interaction with the entangled double atoms.And it is found that with the intensifying of entangle between initial state non-classical properties of photon distribution will increase corresponding,which indicates that non-classical light emission can be generated from the interaction of given entangled double atoms. The time evolution properties of photon distribution in the interaction of entangled double atoms and coherent field are studied by means of numerical calculation.The results show that the coherent field which has not photon anti-bunching and photon sub-Poisson distribution can gain these non-classical properties through the interaction with the entangled double atoms.And it is found that with the intensifying of entangle between initial state non-classical properties of photon distribution will increase corresponding,which indicates that non-classical light emission can be generated from the interaction of given entangled double atoms.
Acta Photonica Sinica
- Publication Date: Sep. 10, 2020
- Vol. 39, Issue 1, 160 (2010)
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