Pub Date : 2020-11-25DOI: 10.1103/PHYSREVRESEARCH.3.013245
Andre G. Campos, K. Hatsagortsyan, C. Keitel
Exact solutions of the Dirac equation, a system of four partial differential equations, are rare. The vast majority of them are for highly symmetric stationary systems. Moreover, only a handful of solutions for time dependent dynamics exists. Given the growing number of applications of high energy electron beams interacting with a variety of quantum systems in laser fields, novel methods for finding exact solutions to the Dirac equation are called for. We present a method for building up solutions to the Dirac equation employing a recently introduced approach for the description of spinorial fields and their driving electromagnetic fields in terms of geometric algebras. We illustrate the method by developing several stationary as well as non-stationary solutions of the Dirac equation with well defined orbital angular momentum along the electron's propagation direction. The first set of solutions describe free electron beams in terms of Bessel functions as well as stationary solutions for both a homogeneous and an inhomogeneous magnetic field. The second set of solutions are new and involve a plane electromagnetic wave combined with a generally inhomogeneous longitudinal magnetic field. Moreover, the developed technique allows us to derive general physical properties of the dynamics in such field configurations, as well as provides physical predictions on the self-consistent electromagnetic fields induced by the dynamics.
{"title":"Construction of Dirac spinors for electron vortex beams in background electromagnetic fields","authors":"Andre G. Campos, K. Hatsagortsyan, C. Keitel","doi":"10.1103/PHYSREVRESEARCH.3.013245","DOIUrl":"https://doi.org/10.1103/PHYSREVRESEARCH.3.013245","url":null,"abstract":"Exact solutions of the Dirac equation, a system of four partial differential equations, are rare. The vast majority of them are for highly symmetric stationary systems. Moreover, only a handful of solutions for time dependent dynamics exists. Given the growing number of applications of high energy electron beams interacting with a variety of quantum systems in laser fields, novel methods for finding exact solutions to the Dirac equation are called for. We present a method for building up solutions to the Dirac equation employing a recently introduced approach for the description of spinorial fields and their driving electromagnetic fields in terms of geometric algebras. We illustrate the method by developing several stationary as well as non-stationary solutions of the Dirac equation with well defined orbital angular momentum along the electron's propagation direction. The first set of solutions describe free electron beams in terms of Bessel functions as well as stationary solutions for both a homogeneous and an inhomogeneous magnetic field. The second set of solutions are new and involve a plane electromagnetic wave combined with a generally inhomogeneous longitudinal magnetic field. Moreover, the developed technique allows us to derive general physical properties of the dynamics in such field configurations, as well as provides physical predictions on the self-consistent electromagnetic fields induced by the dynamics.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90685470","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 : 2020-11-25DOI: 10.1103/physreva.102.063105
J. Wätzel, J. Berakdar
Laser fields can be shaped on a subwavelength scale as to have a specific distribution in spin angular momentum, orbital structure, or topology. We study how these various features affect the strongly nonlinear electron dynamics. Specifically, we derive closed expressions for the wave function of an unbound electron subject to a generally structured, intense laser field and demonstrate its use for imprinting the orbital angular momentum of a propagating optical vortex onto photoelectrons emitted from atoms and traveling through the optical vortex. It is also shown that photoelectrons can be accelerated or momentum textured when moving through a focused, intense laser field whose spin angular momentum is modulated as to have a radial polarization, which also implies the presence of a strong electrical longitudinal component. Further results are presented on the subwavelength spatiotemporal imaging of a laser field topology, as demonstrated explicitly for the field's spin and orbital distributions of lossless propagating optical skyrmions imaged by photoelectrons.
{"title":"Electrons in intense laser fields with local phase, polarization, and skyrmionic textures","authors":"J. Wätzel, J. Berakdar","doi":"10.1103/physreva.102.063105","DOIUrl":"https://doi.org/10.1103/physreva.102.063105","url":null,"abstract":"Laser fields can be shaped on a subwavelength scale as to have a specific distribution in spin angular momentum, orbital structure, or topology. We study how these various features affect the strongly nonlinear electron dynamics. Specifically, we derive closed expressions for the wave function of an unbound electron subject to a generally structured, intense laser field and demonstrate its use for imprinting the orbital angular momentum of a propagating optical vortex onto photoelectrons emitted from atoms and traveling through the optical vortex. It is also shown that photoelectrons can be accelerated or momentum textured when moving through a focused, intense laser field whose spin angular momentum is modulated as to have a radial polarization, which also implies the presence of a strong electrical longitudinal component. Further results are presented on the subwavelength spatiotemporal imaging of a laser field topology, as demonstrated explicitly for the field's spin and orbital distributions of lossless propagating optical skyrmions imaged by photoelectrons.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87038237","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 : 2020-11-24DOI: 10.1103/physreva.102.053721
B. Ann, G. Steele
Superconducting cavities with high quality factors play an essential role in circuit quantum electrodynamics and quantum computing. In measurements of the the intrinsic loss rates of high frequency modes, it can be challenging to design an appropriate coupling to the measurement circuit in such a way that the resulting signal is sufficiently strong but also that this coupling does not lead to unwanted loading circuit, obscuring the intrinsic internal loss rates. Here, we propose and demonstrate a spectroscopic probe of high-Q resonators based on the phenomena of electromagnetically-induced transparency (EIT) between the resonator and qubit in the weak dispersive coupling regime. Applying a sideband drive signal to the qubit, we observe an interference dip originated from EIT in the qubit spectroscopy, originating from the quantum interference between the qubit probe signal and sideband transition. From the width and the depth of the dip, we are able to extract the single-photon linewidth of the resonator from an analytical model. Working in a previously unexplored regime in which the qubit has a larger linewidth than the resonator reduces the technical challenge of making a high-coherence qubit and is advantageous for remaining in the weakly-invasive limit of coupling to the resonator. Furthermore, the sideband and the dispersive coupling between the resonator and the qubit can be tuned $in~situ$ controlling the strength of the sideband drive power. This $in-situ$ tuneability allows the technique to be applied for efficient measurement of the resonator loss rate for any quality factor below a fixed upper bound, on the order of $10^8$ for our device, allowing a wide range of quality factors to probed using a single design.
{"title":"Tunable and weakly invasive probing of a superconducting resonator based on electromagnetically induced transparency","authors":"B. Ann, G. Steele","doi":"10.1103/physreva.102.053721","DOIUrl":"https://doi.org/10.1103/physreva.102.053721","url":null,"abstract":"Superconducting cavities with high quality factors play an essential role in circuit quantum electrodynamics and quantum computing. In measurements of the the intrinsic loss rates of high frequency modes, it can be challenging to design an appropriate coupling to the measurement circuit in such a way that the resulting signal is sufficiently strong but also that this coupling does not lead to unwanted loading circuit, obscuring the intrinsic internal loss rates. Here, we propose and demonstrate a spectroscopic probe of high-Q resonators based on the phenomena of electromagnetically-induced transparency (EIT) between the resonator and qubit in the weak dispersive coupling regime. Applying a sideband drive signal to the qubit, we observe an interference dip originated from EIT in the qubit spectroscopy, originating from the quantum interference between the qubit probe signal and sideband transition. From the width and the depth of the dip, we are able to extract the single-photon linewidth of the resonator from an analytical model. Working in a previously unexplored regime in which the qubit has a larger linewidth than the resonator reduces the technical challenge of making a high-coherence qubit and is advantageous for remaining in the weakly-invasive limit of coupling to the resonator. Furthermore, the sideband and the dispersive coupling between the resonator and the qubit can be tuned $in~situ$ controlling the strength of the sideband drive power. This $in-situ$ tuneability allows the technique to be applied for efficient measurement of the resonator loss rate for any quality factor below a fixed upper bound, on the order of $10^8$ for our device, allowing a wide range of quality factors to probed using a single design.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89714944","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 : 2020-11-24DOI: 10.1103/PhysRevB.103.195443
H. Duarte, H. T. Dinani, V. Jacques, J. Maze
Several efforts have been made to polarize the nearby nuclear environment of nitrogen vacancy (NV) centers for quantum metrology and quantum information applications. Different methods showed different nuclear spin polarization efficiencies and rely on electronic spin polarization associated to the NV center, which in turn crucially depends on the inter-system crossing. Recently, the rates involved in the inter-system crossing have been measured leading to different transition rate models. Here, we consider the effect of these rates on several nuclear polarization methods based on the level anti-crossing, and precession of the nuclear population while the electronic spin is in the ms = 0 and ms = 1 spin states. We show that the nuclear polarization depends on the power of optical excitation used to polarize the electronic spin. The degree of nuclear spin polarization is different for each transition rate model. Therefore, the results presented here are relevant for validating these models and for polarizing nuclear spins. Furthermore, we analyze the performance of each method by considering the nuclear position relative to the symmetry axis of the NV center.
{"title":"Effect of intersystem crossing rates and optical illumination on the polarization of nuclear spins close to nitrogen-vacancy centers","authors":"H. Duarte, H. T. Dinani, V. Jacques, J. Maze","doi":"10.1103/PhysRevB.103.195443","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.195443","url":null,"abstract":"Several efforts have been made to polarize the nearby nuclear environment of nitrogen vacancy (NV) centers for quantum metrology and quantum information applications. Different methods showed different nuclear spin polarization efficiencies and rely on electronic spin polarization associated to the NV center, which in turn crucially depends on the inter-system crossing. Recently, the rates involved in the inter-system crossing have been measured leading to different transition rate models. Here, we consider the effect of these rates on several nuclear polarization methods based on the level anti-crossing, and precession of the nuclear population while the electronic spin is in the ms = 0 and ms = 1 spin states. We show that the nuclear polarization depends on the power of optical excitation used to polarize the electronic spin. The degree of nuclear spin polarization is different for each transition rate model. Therefore, the results presented here are relevant for validating these models and for polarizing nuclear spins. Furthermore, we analyze the performance of each method by considering the nuclear position relative to the symmetry axis of the NV center.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"152 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87581431","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 : 2020-11-23DOI: 10.1103/PHYSREVA.103.042217
Beńıtez Rodŕıguez, Piceno Mart́ınez, L. A. Aguilar
Quantum nonlocality and quantum steering are fundamental correlations of quantum systems which can not be created using classical resources only. Nonlocality describes the ability to influence the possible results of measurements carried out in distant systems, in quantum steering Alice remotely steers Bob's state. Research in nonlocality and steering possess a fundamental interest for the development of quantum information and in many applications requiring nonlocal resources like quantum key distribution. On the other hand, the Stern-Gerlach experiment holds an important place in the history, development and teaching of quantum mechanics and quantum information. In particular, the thought experiment of consecutive Stern-Gerlach Experiments is commonly used to exemplify the concept of non-commutativity between quantum operators. However, to the best of our knowledge, the consecutive Stern-Gerlach Experiments have not been treated in a fully quantum manner yet, and it is a widely accepted idea that atoms crossing consecutive Stern-Gerlach Experiments follow classical paths. Here we demonstrate that two consecutive Stern-Gerach Experiment generate nonlocality and steering, these nonlocal effects strongly modify our usual understanding of this experiment. Also, we discuss the implications of this result and its relation with the entanglement. This suggests the use of quantum correlations, of particles possessing mass, to generate nonlocal taks using this venerable experiment.
{"title":"Single-particle steering and nonlocality: The consecutive Stern-Gerlach experiments","authors":"Beńıtez Rodŕıguez, Piceno Mart́ınez, L. A. Aguilar","doi":"10.1103/PHYSREVA.103.042217","DOIUrl":"https://doi.org/10.1103/PHYSREVA.103.042217","url":null,"abstract":"Quantum nonlocality and quantum steering are fundamental correlations of quantum systems which can not be created using classical resources only. Nonlocality describes the ability to influence the possible results of measurements carried out in distant systems, in quantum steering Alice remotely steers Bob's state. Research in nonlocality and steering possess a fundamental interest for the development of quantum information and in many applications requiring nonlocal resources like quantum key distribution. On the other hand, the Stern-Gerlach experiment holds an important place in the history, development and teaching of quantum mechanics and quantum information. In particular, the thought experiment of consecutive Stern-Gerlach Experiments is commonly used to exemplify the concept of non-commutativity between quantum operators. However, to the best of our knowledge, the consecutive Stern-Gerlach Experiments have not been treated in a fully quantum manner yet, and it is a widely accepted idea that atoms crossing consecutive Stern-Gerlach Experiments follow classical paths. Here we demonstrate that two consecutive Stern-Gerach Experiment generate nonlocality and steering, these nonlocal effects strongly modify our usual understanding of this experiment. Also, we discuss the implications of this result and its relation with the entanglement. This suggests the use of quantum correlations, of particles possessing mass, to generate nonlocal taks using this venerable experiment.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75379691","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 : 2020-11-23DOI: 10.1103/PhysRevApplied.14.054057
Wen‐Qiang Liu, Hai‐Rui Wei, L. Kwek
Effective quantum information processing is tantamount in part to the minimization the quantum resources needed by quantum logic gates. Here, we propose an optimization of an n-controlled-qubit Fredkin gate with a maximum of 2n+1 two-qubit gates and 2n single-qudit gates by exploiting auxiliary Hilbert spaces. The number of logic gates required improves on earlier results on simulating arbitrary n-qubit Fredkin gates. In particular, the optimal result for one-controlled-qubit Fredkin gate (which requires three qutrit-qubit partial-swap gates) breaks the theoretical nonconstructive lower bound of five two-qubit gates. Furthermore, using an additional spatial-mode degree of freedom, we design a possible architecture to implement a polarization-encoded Fredkin gate with linear optical elements.
{"title":"Low-Cost Fredkin Gate with Auxiliary Space","authors":"Wen‐Qiang Liu, Hai‐Rui Wei, L. Kwek","doi":"10.1103/PhysRevApplied.14.054057","DOIUrl":"https://doi.org/10.1103/PhysRevApplied.14.054057","url":null,"abstract":"Effective quantum information processing is tantamount in part to the minimization the quantum resources needed by quantum logic gates. Here, we propose an optimization of an n-controlled-qubit Fredkin gate with a maximum of 2n+1 two-qubit gates and 2n single-qudit gates by exploiting auxiliary Hilbert spaces. The number of logic gates required improves on earlier results on simulating arbitrary n-qubit Fredkin gates. In particular, the optimal result for one-controlled-qubit Fredkin gate (which requires three qutrit-qubit partial-swap gates) breaks the theoretical nonconstructive lower bound of five two-qubit gates. Furthermore, using an additional spatial-mode degree of freedom, we design a possible architecture to implement a polarization-encoded Fredkin gate with linear optical elements.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82232362","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 : 2020-11-23DOI: 10.1103/PHYSREVA.103.012227
Wenting Zhou, Shijing Cheng, Hongwei Yu
We generalize the formalism proposed by Dalibard, Dupont-Roc and Cohen-Tannoudji [the DDC formalism] to the fourth order of the coupling constant, which can be used to study the interatomic interaction of two ground-state atoms coupled with the vacuum scalar fields. We show that the interatomic potential can be attributed to the joint effect of both vacuum fluctuations and the radiation reaction of atoms. Remarkably, the formulae we derived for the contributions of vacuum fluctuations and the radiation reaction to the interatomic potential upon which future research on fourth-order effects in particular circumstances can be based differ from those in the existing literature [Phys. Rev. D 95, 085014 (2017)].
{"title":"Interatomic interaction of two ground-state atoms in vacuum: Contributions of vacuum fluctuations and radiation reaction","authors":"Wenting Zhou, Shijing Cheng, Hongwei Yu","doi":"10.1103/PHYSREVA.103.012227","DOIUrl":"https://doi.org/10.1103/PHYSREVA.103.012227","url":null,"abstract":"We generalize the formalism proposed by Dalibard, Dupont-Roc and Cohen-Tannoudji [the DDC formalism] to the fourth order of the coupling constant, which can be used to study the interatomic interaction of two ground-state atoms coupled with the vacuum scalar fields. We show that the interatomic potential can be attributed to the joint effect of both vacuum fluctuations and the radiation reaction of atoms. Remarkably, the formulae we derived for the contributions of vacuum fluctuations and the radiation reaction to the interatomic potential upon which future research on fourth-order effects in particular circumstances can be based differ from those in the existing literature [Phys. Rev. D 95, 085014 (2017)].","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82435213","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}
Yuri Belousov, R. Grimaudo, A. Messina, A. Migliore, A. Sergi
We propose a method to describe the evolution of two spins coupled by hyperfine interaction in an external time-dependent magnetic field. We apply the approach to the case of hyperfine interaction with axial symmetry, which can be solved exactly in a constant, appropriately oriented magnetic field. In order to treat the nonstationary dynamical problem, we modify the time-dependent Schrodinger equation through a change of representation that, by exploiting an instantaneous (adiabatic) basis makes the time-dependent Hamiltonian diagonal at any time instant. The solution of the transformed time-dependent Schrodinger in the form of chronologically ordered exponents with transparent pre-exponential coefficients is reported. This solution is highly simplified when an adiabatically varying magnetic field perturbs the system. The approach here proposed may be used for the perturbative treatment of other dynamical problems with no exact solution.
{"title":"New approach to describe two coupled spins in a variable magnetic field","authors":"Yuri Belousov, R. Grimaudo, A. Messina, A. Migliore, A. Sergi","doi":"10.1063/5.0055009","DOIUrl":"https://doi.org/10.1063/5.0055009","url":null,"abstract":"We propose a method to describe the evolution of two spins coupled by hyperfine interaction in an external time-dependent magnetic field. We apply the approach to the case of hyperfine interaction with axial symmetry, which can be solved exactly in a constant, appropriately oriented magnetic field. In order to treat the nonstationary dynamical problem, we modify the time-dependent Schrodinger equation through a change of representation that, by exploiting an instantaneous (adiabatic) basis makes the time-dependent Hamiltonian diagonal at any time instant. The solution of the transformed time-dependent Schrodinger in the form of chronologically ordered exponents with transparent pre-exponential coefficients is reported. This solution is highly simplified when an adiabatically varying magnetic field perturbs the system. The approach here proposed may be used for the perturbative treatment of other dynamical problems with no exact solution.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82157663","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 : 2020-11-22DOI: 10.21203/rs.3.rs-125563/v1
B. Ham
Over the last several decades, quantum entanglement has been intensively studied for potential applications in quantum information science. Although intensive studies have progressed for nonlocal correlation, fundamental understanding of entanglement itself is still limited. Here, the quantum feature of anticorrelation, the so-called HOM dip, based on probabilistic entangled photon pairs is analyzed for its fundamental physics and compared with a new method of on-demand entangled photon pair generations using coherent light. The fundamental physics why there is no correlation in HOM dip measurements is answered, and new coherence quantum physics is proposed for macroscopic quantum entanglement generations.
{"title":"On-demand quantum correlation control using coherent photons","authors":"B. Ham","doi":"10.21203/rs.3.rs-125563/v1","DOIUrl":"https://doi.org/10.21203/rs.3.rs-125563/v1","url":null,"abstract":"\u0000 Over the last several decades, quantum entanglement has been intensively studied for potential applications in quantum information science. Although intensive studies have progressed for nonlocal correlation, fundamental understanding of entanglement itself is still limited. Here, the quantum feature of anticorrelation, the so-called HOM dip, based on probabilistic entangled photon pairs is analyzed for its fundamental physics and compared with a new method of on-demand entangled photon pair generations using coherent light. The fundamental physics why there is no correlation in HOM dip measurements is answered, and new coherence quantum physics is proposed for macroscopic quantum entanglement generations.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89944331","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 : 2020-11-21DOI: 10.26226/morressier.5fa409874d4e91fe5c54b993
Pedro Rivero, I. Cloet, Z. Sullivan
The VQE algorithm has turned out to be quite expensive to run given the way we currently access quantum processors (i.e. over the cloud). In order to alleviate this issue, we introduce Quantum Sampling Regression (QSR), an alternative hybrid quantum-classical algorithm, and analyze some of its use cases based on time complexity in the low qubit number regime. In exchange for some extra classical resources, this novel strategy is proved to be optimal in terms of the number of samples it requires from the quantum processor. We develop a simple analytical model to evaluate when this algorithm is more efficient than VQE, and, from the same theoretical considerations, establish a threshold above which quantum advantage can occur. Finally, we demonstrate the efficacy of our algorithm for a benchmark problem.
{"title":"An optimal quantum sampling regression algorithm for variational eigensolving in the low qubit number regime","authors":"Pedro Rivero, I. Cloet, Z. Sullivan","doi":"10.26226/morressier.5fa409874d4e91fe5c54b993","DOIUrl":"https://doi.org/10.26226/morressier.5fa409874d4e91fe5c54b993","url":null,"abstract":"The VQE algorithm has turned out to be quite expensive to run given the way we currently access quantum processors (i.e. over the cloud). In order to alleviate this issue, we introduce Quantum Sampling Regression (QSR), an alternative hybrid quantum-classical algorithm, and analyze some of its use cases based on time complexity in the low qubit number regime. In exchange for some extra classical resources, this novel strategy is proved to be optimal in terms of the number of samples it requires from the quantum processor. We develop a simple analytical model to evaluate when this algorithm is more efficient than VQE, and, from the same theoretical considerations, establish a threshold above which quantum advantage can occur. Finally, we demonstrate the efficacy of our algorithm for a benchmark problem.","PeriodicalId":8484,"journal":{"name":"arXiv: Quantum Physics","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87513950","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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