Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/041
Hai-bo Wang, S. Odate, Yongmin Li, Takayoshi Kobayashi
We analyse the output characteristic of a quantum high-pass/low-pass filter, which was introduced recently (Wang et al 2005 Phys. Rev. A 72 013822). Various responses of quantum filters with different parameters have been calculated. It is possible to apply these quantum circuits in quantum state preparation.
我们分析了最近引入的量子高通/低通滤波器的输出特性(Wang et al . 2005 Phys)。Rev. A 72 013822)。计算了不同参数下量子滤波器的各种响应。将这些量子电路应用于量子态制备是可能的。
{"title":"The response characteristic of a quantum high-pass/low-pass filter for quantum state preparation","authors":"Hai-bo Wang, S. Odate, Yongmin Li, Takayoshi Kobayashi","doi":"10.1088/1464-4266/7/12/041","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/041","url":null,"abstract":"We analyse the output characteristic of a quantum high-pass/low-pass filter, which was introduced recently (Wang et al 2005 Phys. Rev. A 72 013822). Various responses of quantum filters with different parameters have been calculated. It is possible to apply these quantum circuits in quantum state preparation.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/041","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60915930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/017
H. Brandt
It is argued that the BB84 (Bennett–Brassard 1984) protocol of quantum key distribution has a vulnerability similar to the well-known vulnerability of the B92 (Bennett 1992) protocol in the presence of losses. The quantum circuit and design are first reviewed for an optimized entangling probe attacking the BB84 protocol of quantum key distribution and yielding maximum information to the probe. Probe photon polarization states become optimally entangled with the signal states on their way between the legitimate transmitter and receiver. Although standard von Neumann projective measurements of the probe yield maximum information on the pre-privacy amplified key, if instead the probe measurements are performed with a certain positive operator valued measure, then the measurement results are unambiguous, at least some of the time, resulting in complete information gain by the probe for sufficient loss in the key distribution channel.
{"title":"Conclusive eavesdropping in quantum key distribution","authors":"H. Brandt","doi":"10.1088/1464-4266/7/12/017","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/017","url":null,"abstract":"It is argued that the BB84 (Bennett–Brassard 1984) protocol of quantum key distribution has a vulnerability similar to the well-known vulnerability of the B92 (Bennett 1992) protocol in the presence of losses. The quantum circuit and design are first reviewed for an optimized entangling probe attacking the BB84 protocol of quantum key distribution and yielding maximum information to the probe. Probe photon polarization states become optimally entangled with the signal states on their way between the legitimate transmitter and receiver. Although standard von Neumann projective measurements of the probe yield maximum information on the pre-privacy amplified key, if instead the probe measurements are performed with a certain positive operator valued measure, then the measurement results are unambiguous, at least some of the time, resulting in complete information gain by the probe for sufficient loss in the key distribution channel.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/017","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60914295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/014
F. A. Raffa, M. Rasetti
Our investigation concerns the class of Josephson-like systems, sharing the same nonlinear Hamiltonian. Among the latter a Josephson junction with an external biasing circuit is considered. We diagonalize the fully nonlinear Hamiltonian (in the superconductive regime of the junction) in the Fock space of the TBHA (two-boson Heisenberg algebra) and prove that such algebra leads quite naturally to the theoretical realization of codewords and logical operators: the codewords are defined as the even and odd coherent states of the TBHA, while the logical operators are expressed in terms of operators in the same algebra. Our theoretical construction corresponds to a continuous variable quantum computation scheme; the continuous variables are identified in terms of the physical operators of the junction. The link between this scheme and the technique of fermionization of bosonic systems is also discussed.
{"title":"Two-boson algebra and quantum computing with Josephson-like systems","authors":"F. A. Raffa, M. Rasetti","doi":"10.1088/1464-4266/7/12/014","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/014","url":null,"abstract":"Our investigation concerns the class of Josephson-like systems, sharing the same nonlinear Hamiltonian. Among the latter a Josephson junction with an external biasing circuit is considered. We diagonalize the fully nonlinear Hamiltonian (in the superconductive regime of the junction) in the Fock space of the TBHA (two-boson Heisenberg algebra) and prove that such algebra leads quite naturally to the theoretical realization of codewords and logical operators: the codewords are defined as the even and odd coherent states of the TBHA, while the logical operators are expressed in terms of operators in the same algebra. Our theoretical construction corresponds to a continuous variable quantum computation scheme; the continuous variables are identified in terms of the physical operators of the junction. The link between this scheme and the technique of fermionization of bosonic systems is also discussed.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/014","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60914642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/028
A. Obada, G. M. A. Al-Kader
Nonlinear extensions of the single-mode squeezed vacuum and squeezed coherent states are constructed. Nonlinear squeezed coherent states (NLSCSs) are defined and special cases of these states are discussed. Two cases of the definition are considered for the unitary and non-unitary deformation operator functions. Some nonclassical properties of these states are discussed. The Glauber second-order coherence function is calculated. Analytical and numerical results for the quadrature component distributions for the NLSCSs are presented. The s-parameterized quasi-probability function, especially the Wigner function, is discussed.
{"title":"A class of nonlinear squeezed coherent states","authors":"A. Obada, G. M. A. Al-Kader","doi":"10.1088/1464-4266/7/12/028","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/028","url":null,"abstract":"Nonlinear extensions of the single-mode squeezed vacuum and squeezed coherent states are constructed. Nonlinear squeezed coherent states (NLSCSs) are defined and special cases of these states are discussed. Two cases of the definition are considered for the unitary and non-unitary deformation operator functions. Some nonclassical properties of these states are discussed. The Glauber second-order coherence function is calculated. Analytical and numerical results for the quadrature component distributions for the NLSCSs are presented. The s-parameterized quasi-probability function, especially the Wigner function, is discussed.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60914914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/030
S. Dagach
In this paper a universal quantum copying machine is proposed in a cavity quantum electrodynamic experiment using local control-NOT gates with an external field in the dispersive regime, in a scheme based on two high-Q cavities.
{"title":"Proposal for a universal quantum copying machine in cavity QED via a dispersive interaction","authors":"S. Dagach","doi":"10.1088/1464-4266/7/12/030","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/030","url":null,"abstract":"In this paper a universal quantum copying machine is proposed in a cavity quantum electrodynamic experiment using local control-NOT gates with an external field in the dispersive regime, in a scheme based on two high-Q cavities.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/030","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60915199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/043
A. Alodjants, A. Y. Leksin, S. Arakelian
We consider a new approach for describing a quantum optical Bose system with internal Gell-Mann symmetry by means of the SU(3) symmetry polarization map in Hilbert space. The operational measurement of the density (or coherency) matrix elements for the three-mode optical field is discussed for the first time. We have introduced a set of operators that describe the quantum measurement procedure and the behaviour of fluctuations for the amplitude and phase characteristics of the three-level system. A novel twelve-port interferometer for making parallel measurements of the Gell-Mann parameters is proposed. The quantum properties of qutrit W-states in the measurement procedure are examined.
{"title":"Quantum operational measurement of amplitude and phase parameters for SU(3) symmetry optical fields","authors":"A. Alodjants, A. Y. Leksin, S. Arakelian","doi":"10.1088/1464-4266/7/12/043","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/043","url":null,"abstract":"We consider a new approach for describing a quantum optical Bose system with internal Gell-Mann symmetry by means of the SU(3) symmetry polarization map in Hilbert space. The operational measurement of the density (or coherency) matrix elements for the three-mode optical field is discussed for the first time. We have introduced a set of operators that describe the quantum measurement procedure and the behaviour of fluctuations for the amplitude and phase characteristics of the three-level system. A novel twelve-port interferometer for making parallel measurements of the Gell-Mann parameters is proposed. The quantum properties of qutrit W-states in the measurement procedure are examined.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/043","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60916040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/008
M. Planat, M. Saniga
Coding, transmission and recovery of quantum states with high security and efficiency, and with as low fluctuations as possible, is the main goal of quantum information protocols and their proper technical implementations. The paper deals with this topic, focusing on the quantum states related to Galois algebras. We first review the constructions of complete sets of mutually unbiased bases in a Hilbert space of dimension q = pm, with p being a prime and m a positive integer, employing the properties of Galois fields Fq (for p>2) and/or Galois rings of characteristic four R4m (for p = 2). We then discuss the Gauss sums and their role in describing quantum phase fluctuations. Finally, we examine an intricate connection between the concepts of mutual unbiasedness and maximal entanglement.
{"title":"Galois algebras of squeezed quantum phase states","authors":"M. Planat, M. Saniga","doi":"10.1088/1464-4266/7/12/008","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/008","url":null,"abstract":"Coding, transmission and recovery of quantum states with high security and efficiency, and with as low fluctuations as possible, is the main goal of quantum information protocols and their proper technical implementations. The paper deals with this topic, focusing on the quantum states related to Galois algebras. We first review the constructions of complete sets of mutually unbiased bases in a Hilbert space of dimension q = pm, with p being a prime and m a positive integer, employing the properties of Galois fields Fq (for p>2) and/or Galois rings of characteristic four R4m (for p = 2). We then discuss the Gauss sums and their role in describing quantum phase fluctuations. Finally, we examine an intricate connection between the concepts of mutual unbiasedness and maximal entanglement.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60914186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/035
M. Khanbekyan, D. Welsch, A. Semenov, W. V. F. Jena, H Germany, I. Physics, Kiev, Ukraine, U. Rostock
The quantized electromagnetic field inside and outside an absorbing high-Q cavity is studied, with special emphasis on the absorption losses in the coupling mirror and their influence on the outgoing field. Generalized operator input?output relations are derived, which are used to calculate the Wigner function of the outgoing field. To illustrate the theory, the preparation of the outgoing field in a Schr?dinger cat-like state is discussed.
{"title":"Quantum-state input–output relations for absorbing cavities","authors":"M. Khanbekyan, D. Welsch, A. Semenov, W. V. F. Jena, H Germany, I. Physics, Kiev, Ukraine, U. Rostock","doi":"10.1088/1464-4266/7/12/035","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/035","url":null,"abstract":"The quantized electromagnetic field inside and outside an absorbing high-Q cavity is studied, with special emphasis on the absorption losses in the coupling mirror and their influence on the outgoing field. Generalized operator input?output relations are derived, which are used to calculate the Wigner function of the outgoing field. To illustrate the theory, the preparation of the outgoing field in a Schr?dinger cat-like state is discussed.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/035","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60915380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/047
N. Nayak, R. N. Deb, B. Dutta-Roy
We show that squeezed spin states achieved through nonlinear interactions are eigenstates of a non-Hermitian operator, which however enjoys the property of pseudo-Hermiticity such that the resulting eigenvalues are real. We represent the squeezed states in terms of Wigner d-matrices, making the evaluation of squeezing straightforward. We show that the spin squeezing can go up to 70%.
{"title":"Squeezed spin states and pseudo-Hermitian operators","authors":"N. Nayak, R. N. Deb, B. Dutta-Roy","doi":"10.1088/1464-4266/7/12/047","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/047","url":null,"abstract":"We show that squeezed spin states achieved through nonlinear interactions are eigenstates of a non-Hermitian operator, which however enjoys the property of pseudo-Hermiticity such that the resulting eigenvalues are real. We represent the squeezed states in terms of Wigner d-matrices, making the evaluation of squeezing straightforward. We show that the spin squeezing can go up to 70%.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/047","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60916213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1088/1464-4266/7/12/018
V. Peřinová, A. Luks
It is familiar that a well behaved operator of the harmonic oscillator phase does not exist. Therefore, Turski's phase operator and the operator of Garrison and Wong may be at most defined in an interesting fashion and yield useful quantum expectation values. In this paper we touch on a recent incomplete definition of a phase operator which has also failed in the respect that it can be completed only to a definition of an 'incomplete' phase operator. We discuss, however, a possibility of completion of the definition and a relationship to the phase operator from an s-parametrized quasidistribution.
{"title":"Quantum phase from s-parametrized quasidistributions","authors":"V. Peřinová, A. Luks","doi":"10.1088/1464-4266/7/12/018","DOIUrl":"https://doi.org/10.1088/1464-4266/7/12/018","url":null,"abstract":"It is familiar that a well behaved operator of the harmonic oscillator phase does not exist. Therefore, Turski's phase operator and the operator of Garrison and Wong may be at most defined in an interesting fashion and yield useful quantum expectation values. In this paper we touch on a recent incomplete definition of a phase operator which has also failed in the respect that it can be completed only to a definition of an 'incomplete' phase operator. We discuss, however, a possibility of completion of the definition and a relationship to the phase operator from an s-parametrized quasidistribution.","PeriodicalId":87441,"journal":{"name":"Journal of optics. B, Quantum and semiclassical optics : journal of the European Optical Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1464-4266/7/12/018","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60914374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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