Pub Date : 2024-08-14DOI: 10.1088/1367-2630/ad6bb8
Yan Xin Rong, Shuo Wang, Zhen Fei Zhang, Yong Jian Gu, Ya Xiao
Recently, both global and local classical randomness-assisted projective measurement protocols have been employed to share Bell nonlocality of an entangled state among multiple sequential parties. Unlike Bell nonlocality, Einstein–Podolsky–Rosen (EPR) steering exhibits distinct asymmetric characteristics and serves as the necessary quantum resource for one-sided device-independent quantum information tasks. In this work, we propose a projective measurement protocol and investigate the shareability of EPR steering with steering radius criterion theoretically and experimentally. Our results reveal that arbitrarily many independent parties can share one-way steerability using projective measurements, even when no shared randomness is available. Furthermore, by leveraging only local randomness, asymmetric two-way steerability can also be shared. Our work not only deepens the understanding of the role of projective measurements in sharing quantum correlations but also opens up a new avenue for reutilizing asymmetric quantum correlations.
{"title":"Sharing asymmetric Einstein–Podolsky–Rosen steering with projective measurements","authors":"Yan Xin Rong, Shuo Wang, Zhen Fei Zhang, Yong Jian Gu, Ya Xiao","doi":"10.1088/1367-2630/ad6bb8","DOIUrl":"https://doi.org/10.1088/1367-2630/ad6bb8","url":null,"abstract":"Recently, both global and local classical randomness-assisted projective measurement protocols have been employed to share Bell nonlocality of an entangled state among multiple sequential parties. Unlike Bell nonlocality, Einstein–Podolsky–Rosen (EPR) steering exhibits distinct asymmetric characteristics and serves as the necessary quantum resource for one-sided device-independent quantum information tasks. In this work, we propose a projective measurement protocol and investigate the shareability of EPR steering with steering radius criterion theoretically and experimentally. Our results reveal that arbitrarily many independent parties can share one-way steerability using projective measurements, even when no shared randomness is available. Furthermore, by leveraging only local randomness, asymmetric two-way steerability can also be shared. Our work not only deepens the understanding of the role of projective measurements in sharing quantum correlations but also opens up a new avenue for reutilizing asymmetric quantum correlations.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"274 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-14DOI: 10.1088/1367-2630/ad6a7b
Federico Gallina, Matteo Bruschi, Barbara Fresch
The unraveling of open quantum system dynamics in terms of stochastic quantum trajectories offers a picture of open system dynamics that consistently considers memory effects stemming from the finite correlation time of environment fluctuations. These fluctuations significantly influence the coherence and energy transport properties of excitonic systems. When their correlation time is comparable to the timescale of the Hamiltonian evolution, it leads to the departure of open system dynamics from the Markovian limit. In this work, we leverage the unraveling of exciton dynamics through stochastic Hamiltonian propagators to design quantum circuits that simulate exciton transport, capturing finite memory effects. In addition to enabling the synthesis of parametrizable quantum circuits, stochastic unitary propagators provide a transparent framework for investigating non-Markovian effects on exciton transport. Our analysis reveals a nuanced relationship between environment correlation time and transport efficiency, identifying a regime of ‘memory-assisted’ quantum transport where time-correlated fluctuations allow the system to reach higher efficiency. However, this property is not universal and can only be realized in conjunction with specific features of the system Hamiltonian.
{"title":"From stochastic Hamiltonian to quantum simulation: exploring memory effects in exciton dynamics","authors":"Federico Gallina, Matteo Bruschi, Barbara Fresch","doi":"10.1088/1367-2630/ad6a7b","DOIUrl":"https://doi.org/10.1088/1367-2630/ad6a7b","url":null,"abstract":"The unraveling of open quantum system dynamics in terms of stochastic quantum trajectories offers a picture of open system dynamics that consistently considers memory effects stemming from the finite correlation time of environment fluctuations. These fluctuations significantly influence the coherence and energy transport properties of excitonic systems. When their correlation time is comparable to the timescale of the Hamiltonian evolution, it leads to the departure of open system dynamics from the Markovian limit. In this work, we leverage the unraveling of exciton dynamics through stochastic Hamiltonian propagators to design quantum circuits that simulate exciton transport, capturing finite memory effects. In addition to enabling the synthesis of parametrizable quantum circuits, stochastic unitary propagators provide a transparent framework for investigating non-Markovian effects on exciton transport. Our analysis reveals a nuanced relationship between environment correlation time and transport efficiency, identifying a regime of ‘memory-assisted’ quantum transport where time-correlated fluctuations allow the system to reach higher efficiency. However, this property is not universal and can only be realized in conjunction with specific features of the system Hamiltonian.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"118 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-14DOI: 10.1088/1367-2630/ad6c78
Qin He, Da-Shuai Ma, Botao Fu, Xiao-Ping Li
Employing a combination of first-principles calculations and low-energy effective models, we present a comprehensive investigation on the electronic structure of Pb10(PO4)6O4, which exhibits remarkable quasi-one-dimensional topological flat-band around the Fermi level. These flat bands predominantly originate from the px/py orbitals of the oxygen molecules chain at the fully-occupied 4e Wyckoff positions and thus can be well-captured by a minimal four-band tight-binding model. Furthermore, the abundant crystal symmetry inherent in Pb10(PO4)6O4 provides an ideal platform for the emergence of various quasi-fermions characterized by different dispersion, degeneracy, and dimensionality. These include a 0D four-fold degenerate Dirac fermion exhibiting quadratic dispersion, a 1D quadratic/linear nodal-line fermion along symmetric k-paths, a 1D hourglass nodal-line (HNL) fermion associated with the Dirac fermion, and a 2D symmetry-enforced nodal surface located on the kz = π plane. Moreover, when considering the weak ferromagnetic order, Pb10(PO4)6O4 transforms into a rare semi-half-metal, which is characterized by the presence of Dirac fermion and HNL fermion at the Fermi level for a single spin channel exhibiting 100% spin polarization. Our findings reveal the rarely coexistence of flat bands, diverse topological semimetal states and ferromagnetism in Pb10(PO4)6O4, which may provide valuable insights for further exploring the intriguing interplay between superconductivity and exotic electronic states.
{"title":"Flat-band and diverse quasi-fermions in Pb10(PO4)6O4","authors":"Qin He, Da-Shuai Ma, Botao Fu, Xiao-Ping Li","doi":"10.1088/1367-2630/ad6c78","DOIUrl":"https://doi.org/10.1088/1367-2630/ad6c78","url":null,"abstract":"Employing a combination of first-principles calculations and low-energy effective models, we present a comprehensive investigation on the electronic structure of Pb<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>O<sub>4</sub>, which exhibits remarkable quasi-one-dimensional topological flat-band around the Fermi level. These flat bands predominantly originate from the <inline-formula>\u0000<tex-math><?CDATA $p_x/p_y$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>p</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:msub><mml:mi>p</mml:mi><mml:mi>y</mml:mi></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"njpad6c78ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> orbitals of the oxygen molecules chain at the fully-occupied 4<italic toggle=\"yes\">e</italic> Wyckoff positions and thus can be well-captured by a minimal four-band tight-binding model. Furthermore, the abundant crystal symmetry inherent in Pb<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>O<sub>4</sub> provides an ideal platform for the emergence of various quasi-fermions characterized by different dispersion, degeneracy, and dimensionality. These include a 0D four-fold degenerate Dirac fermion exhibiting quadratic dispersion, a 1D quadratic/linear nodal-line fermion along symmetric <italic toggle=\"yes\">k</italic>-paths, a 1D hourglass nodal-line (HNL) fermion associated with the Dirac fermion, and a 2D symmetry-enforced nodal surface located on the <italic toggle=\"yes\">k<sub>z</sub>\u0000</italic> = <italic toggle=\"yes\">π</italic> plane. Moreover, when considering the weak ferromagnetic order, Pb<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>O<sub>4</sub> transforms into a rare semi-half-metal, which is characterized by the presence of Dirac fermion and HNL fermion at the Fermi level for a single spin channel exhibiting 100<inline-formula>\u0000<tex-math><?CDATA $%$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">%</mml:mi></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"njpad6c78ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> spin polarization. Our findings reveal the rarely coexistence of flat bands, diverse topological semimetal states and ferromagnetism in Pb<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>O<sub>4</sub>, which may provide valuable insights for further exploring the intriguing interplay between superconductivity and exotic electronic states.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"5 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-11DOI: 10.1088/1367-2630/ad6475
David Barral, Mathieu Isoard, Giacomo Sorelli, Manuel Gessner, Nicolas Treps and Mattia Walschaers
Entanglement and non-Gaussianity are physical resources that are essential for a large number of quantum-optics protocols. Non-Gaussian entanglement is indispensable for quantum-computing advantage and outperforms its Gaussian counterparts in a number of quantum-information protocols. The characterization of non-Gaussian entanglement is a critical matter as it is in general highly demanding in terms of resources. We propose a simple protocol based on the Fisher information for witnessing entanglement in an important class of non-Gaussian entangled states: photon-subtracted states. We demonstrate that our protocol is relevant for the detection of non-Gaussian entanglement generated by multiple photon-subtraction and that it is experimentally feasible through homodyne detection.
{"title":"Metrological detection of entanglement generated by non-Gaussian operations","authors":"David Barral, Mathieu Isoard, Giacomo Sorelli, Manuel Gessner, Nicolas Treps and Mattia Walschaers","doi":"10.1088/1367-2630/ad6475","DOIUrl":"https://doi.org/10.1088/1367-2630/ad6475","url":null,"abstract":"Entanglement and non-Gaussianity are physical resources that are essential for a large number of quantum-optics protocols. Non-Gaussian entanglement is indispensable for quantum-computing advantage and outperforms its Gaussian counterparts in a number of quantum-information protocols. The characterization of non-Gaussian entanglement is a critical matter as it is in general highly demanding in terms of resources. We propose a simple protocol based on the Fisher information for witnessing entanglement in an important class of non-Gaussian entangled states: photon-subtracted states. We demonstrate that our protocol is relevant for the detection of non-Gaussian entanglement generated by multiple photon-subtraction and that it is experimentally feasible through homodyne detection.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"3 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-11DOI: 10.1088/1367-2630/ad6703
Kim Fook Lee, Gamze Gül, Zhao Jim and Prem Kumar
We report a fiber loop quantum buffer based on a low-loss 2 × 2 switch and a unit delay made of a fiber delay line. We characterize the device by using a two-photon polarization entangled state in which one photon of the entangled photon pair is stored and retrieved at a repetition rate up to 78 kHz. The device, which enables integer multiples of a unit delay, can store the qubit state in a unit of fiber delay line up to 5.4 km and the number of loop round-trips up to 3. Furthermore, we configure the device with other active elements to realize integer multiplier and divider of a unit delay of a qubit. The quantum state tomography is performed on the retrieved photon and its entangled photon. We obtain a state fidelity 94 with a maximum storage time of 52 s with an insertion loss of 5.56 dB. To further characterize the storing and retrieving processes of the device, we perform entanglement-assisted quantum process tomography on the buffered qubit state. The process fidelity of the device is 0.98. Our result implies that the device preserves the superposition and entanglement of a qubit state from a two-photon polarization-entangled state. This is a significant step towards facilitating applications in optical asynchronous transfer mode based quantum networks.
{"title":"Fiber loop quantum buffer for photonic qubits","authors":"Kim Fook Lee, Gamze Gül, Zhao Jim and Prem Kumar","doi":"10.1088/1367-2630/ad6703","DOIUrl":"https://doi.org/10.1088/1367-2630/ad6703","url":null,"abstract":"We report a fiber loop quantum buffer based on a low-loss 2 × 2 switch and a unit delay made of a fiber delay line. We characterize the device by using a two-photon polarization entangled state in which one photon of the entangled photon pair is stored and retrieved at a repetition rate up to 78 kHz. The device, which enables integer multiples of a unit delay, can store the qubit state in a unit of fiber delay line up to 5.4 km and the number of loop round-trips up to 3. Furthermore, we configure the device with other active elements to realize integer multiplier and divider of a unit delay of a qubit. The quantum state tomography is performed on the retrieved photon and its entangled photon. We obtain a state fidelity 94 with a maximum storage time of 52 s with an insertion loss of 5.56 dB. To further characterize the storing and retrieving processes of the device, we perform entanglement-assisted quantum process tomography on the buffered qubit state. The process fidelity of the device is 0.98. Our result implies that the device preserves the superposition and entanglement of a qubit state from a two-photon polarization-entangled state. This is a significant step towards facilitating applications in optical asynchronous transfer mode based quantum networks.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"75 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-11DOI: 10.1088/1367-2630/ad6a7c
Arvin Gopal Subramaniam, Manoj Kumar, Shashi Thutupalli and Rajesh Singh
Active matter systems—such as a collection of active colloidal particles—operate far from equilibrium with complex inter-particle interactions that govern their collective dynamics. Predicting the collective dynamics of such systems may aid the design of self-shaping structures comprised of active colloidal units with a prescribed dynamical function. Here, using simulations and theory, we study the collective dynamics of a chain consisting of active Brownian particles with internal interactions via trail-mediated chemicals, connected by harmonic springs in two dimensions to obtain design principles for active colloidal molecules. We show that two-dimensional confinement and chemo-repulsive interactions between the freely-jointed particles lead to an emergent rigidity of the chain in the steady-state dynamics. In the chemo-attractive regime, the chain collapses into crystals that abruptly halt their motion. Further, in a chain consisting of a binary mixture of monomers, we show that non-reciprocal chemical affinities between distinct species give rise to novel phenomena, such as chiral molecules with tunable dynamics, sustained undulatory gaits and reversal of the direction of motion. Our results suggest a novel interpretation of the role of trail-mediated interactions, in addition to providing active self-assembly principles arising due to non-reciprocal interactions.
{"title":"Rigid flocks, undulatory gaits, and chiral foldamers in a chemically active polymer","authors":"Arvin Gopal Subramaniam, Manoj Kumar, Shashi Thutupalli and Rajesh Singh","doi":"10.1088/1367-2630/ad6a7c","DOIUrl":"https://doi.org/10.1088/1367-2630/ad6a7c","url":null,"abstract":"Active matter systems—such as a collection of active colloidal particles—operate far from equilibrium with complex inter-particle interactions that govern their collective dynamics. Predicting the collective dynamics of such systems may aid the design of self-shaping structures comprised of active colloidal units with a prescribed dynamical function. Here, using simulations and theory, we study the collective dynamics of a chain consisting of active Brownian particles with internal interactions via trail-mediated chemicals, connected by harmonic springs in two dimensions to obtain design principles for active colloidal molecules. We show that two-dimensional confinement and chemo-repulsive interactions between the freely-jointed particles lead to an emergent rigidity of the chain in the steady-state dynamics. In the chemo-attractive regime, the chain collapses into crystals that abruptly halt their motion. Further, in a chain consisting of a binary mixture of monomers, we show that non-reciprocal chemical affinities between distinct species give rise to novel phenomena, such as chiral molecules with tunable dynamics, sustained undulatory gaits and reversal of the direction of motion. Our results suggest a novel interpretation of the role of trail-mediated interactions, in addition to providing active self-assembly principles arising due to non-reciprocal interactions.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"17 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-11DOI: 10.1088/1367-2630/ad678d
Alessio Belenchia, Felix Spengler, Dennis Rätzel and Daniel Braun
That light propagating in a gravitational field gets frequency-shifted is one of the basic consequences of any metric theory of gravity rooted in the equivalence principle. At the same time, also a time dependent material’s refractive index can frequency-shift light propagating in it. The mathematical analogy between the two effects is such that the latter has been used to study the optical analogue of a black-hole spacetime. Here, we combine these two effects by showing that light propagation in non-linear media in the presence of a moving refractive index perturbation can lead to a gravity-dependent blueshift. We find that the predicted blueshift surpasses the gravitational redshift even if the medium is considered to be perfectly stiff. In realistic scenarios, by far the strongest frequency shift arises due to the deformation of the dielectric medium and the corresponding photoelastic change of refractive index. This has the potential to facilitate optical sensing of small gravity gradients.
{"title":"Non-linear media in weakly curved spacetime: optical solitons and probe pulses for gravimetry","authors":"Alessio Belenchia, Felix Spengler, Dennis Rätzel and Daniel Braun","doi":"10.1088/1367-2630/ad678d","DOIUrl":"https://doi.org/10.1088/1367-2630/ad678d","url":null,"abstract":"That light propagating in a gravitational field gets frequency-shifted is one of the basic consequences of any metric theory of gravity rooted in the equivalence principle. At the same time, also a time dependent material’s refractive index can frequency-shift light propagating in it. The mathematical analogy between the two effects is such that the latter has been used to study the optical analogue of a black-hole spacetime. Here, we combine these two effects by showing that light propagation in non-linear media in the presence of a moving refractive index perturbation can lead to a gravity-dependent blueshift. We find that the predicted blueshift surpasses the gravitational redshift even if the medium is considered to be perfectly stiff. In realistic scenarios, by far the strongest frequency shift arises due to the deformation of the dielectric medium and the corresponding photoelastic change of refractive index. This has the potential to facilitate optical sensing of small gravity gradients.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"13 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-08DOI: 10.1088/1367-2630/ad692a
Pronoy Das, Sathwik Bharadwaj and Zubin Jacob
Spatiotemporal Optical Vortices (STOVs) are structured electromagnetic fields propagating in free space with phase singularities in the space-time domain. Depending on the tilt of the helical phase front, STOVs can carry both longitudinal and transverse orbital angular momentum (OAM). Although STOVs have gained significant interest in the recent years, the current understanding is limited to the semi-classical picture. Here, we develop a quantum theory for STOVs with an arbitrary tilt, extending beyond the paraxial limit. We demonstrate that quantum STOV states, such as Fock and coherent twisted photon pulses, display non-vanishing longitudinal OAM fluctuations that are absent in conventional monochromatic twisted pulses. We show that these quantum fluctuations exhibit a unique texture, i.e. a spatial distribution which can be used to experimentally isolate these quantum effects. Our findings represent a step towards the exploitation of quantum effects of structured light for various applications such as OAM-based encoding protocols and platforms to explore novel light–matter interaction in 2D material systems.
{"title":"Quantum theory of orbital angular momentum in spatiotemporal optical vortices","authors":"Pronoy Das, Sathwik Bharadwaj and Zubin Jacob","doi":"10.1088/1367-2630/ad692a","DOIUrl":"https://doi.org/10.1088/1367-2630/ad692a","url":null,"abstract":"Spatiotemporal Optical Vortices (STOVs) are structured electromagnetic fields propagating in free space with phase singularities in the space-time domain. Depending on the tilt of the helical phase front, STOVs can carry both longitudinal and transverse orbital angular momentum (OAM). Although STOVs have gained significant interest in the recent years, the current understanding is limited to the semi-classical picture. Here, we develop a quantum theory for STOVs with an arbitrary tilt, extending beyond the paraxial limit. We demonstrate that quantum STOV states, such as Fock and coherent twisted photon pulses, display non-vanishing longitudinal OAM fluctuations that are absent in conventional monochromatic twisted pulses. We show that these quantum fluctuations exhibit a unique texture, i.e. a spatial distribution which can be used to experimentally isolate these quantum effects. Our findings represent a step towards the exploitation of quantum effects of structured light for various applications such as OAM-based encoding protocols and platforms to explore novel light–matter interaction in 2D material systems.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"103 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-07DOI: 10.1088/1367-2630/ad69b8
Iason A Sofos, Sara Kanzi and Benjamin T H Varcoe
The generalised second law of black hole thermodynamics states that the sum of a black hole’s entropy and the entropy of all matter outside the black hole cannot decrease with time. The violation of the generalised second law via the process in which a distant observer extracts work by lowering a box arbitrarily close to the event horizon of a black hole has two profound ramifications: (1) that the entropy of the Universe can be decreased arbitrarily via this process; and (2) that it is not appropriate to apply the laws of thermodynamics to systems containing black holes. In this paper, we argue that for the generalised second law to not be violated, entropy must be produced during the lowering process. To demonstrate this, we begin by deriving an equation for the locally measured temperature of the vacuum state of an observer that is a finite distance from the event horizon of a Schwarzschild black hole. Then, using this locally measured temperature and the Unruh effect, we derive an equation for the force required to hold this observer in a stationary position relative to a Schwarzschild black hole. These equations form a framework for calculating the change in black hole entropy as a result of the lowering process both in the case where the process is isentropic and in the case where entropy is produced during the lowering process. In the latter case, two requirements: (1) that the resultant change in black hole entropy is finite; and (2) that the resultant change in common entropy is finite, are used to identify two conditions that the form of an entropy production function must satisfy. These, in turn, are used to identify a set of possible functions describing the production of entropy. Using this set of functions, we demonstrate that the production of entropy limits the amount of work that the distant observer can extract from the lowering process. We find that this allows for the generalised second law to be preserved, provided that a coefficient in this set of functions satisfies a given bound. To conclude, we discuss two natural choices of this coefficient that allow for the generalised second law to be preserved in this lowering process. In addition to providing a resolution to this violation of the generalised second law, the framework presented in this paper can be applied to inform theories of gravity and quantum gravity on the form of their entropy relations, such that they do not violate the generalised second law.
{"title":"Entropy production and the generalised second law of black hole thermodynamics","authors":"Iason A Sofos, Sara Kanzi and Benjamin T H Varcoe","doi":"10.1088/1367-2630/ad69b8","DOIUrl":"https://doi.org/10.1088/1367-2630/ad69b8","url":null,"abstract":"The generalised second law of black hole thermodynamics states that the sum of a black hole’s entropy and the entropy of all matter outside the black hole cannot decrease with time. The violation of the generalised second law via the process in which a distant observer extracts work by lowering a box arbitrarily close to the event horizon of a black hole has two profound ramifications: (1) that the entropy of the Universe can be decreased arbitrarily via this process; and (2) that it is not appropriate to apply the laws of thermodynamics to systems containing black holes. In this paper, we argue that for the generalised second law to not be violated, entropy must be produced during the lowering process. To demonstrate this, we begin by deriving an equation for the locally measured temperature of the vacuum state of an observer that is a finite distance from the event horizon of a Schwarzschild black hole. Then, using this locally measured temperature and the Unruh effect, we derive an equation for the force required to hold this observer in a stationary position relative to a Schwarzschild black hole. These equations form a framework for calculating the change in black hole entropy as a result of the lowering process both in the case where the process is isentropic and in the case where entropy is produced during the lowering process. In the latter case, two requirements: (1) that the resultant change in black hole entropy is finite; and (2) that the resultant change in common entropy is finite, are used to identify two conditions that the form of an entropy production function must satisfy. These, in turn, are used to identify a set of possible functions describing the production of entropy. Using this set of functions, we demonstrate that the production of entropy limits the amount of work that the distant observer can extract from the lowering process. We find that this allows for the generalised second law to be preserved, provided that a coefficient in this set of functions satisfies a given bound. To conclude, we discuss two natural choices of this coefficient that allow for the generalised second law to be preserved in this lowering process. In addition to providing a resolution to this violation of the generalised second law, the framework presented in this paper can be applied to inform theories of gravity and quantum gravity on the form of their entropy relations, such that they do not violate the generalised second law.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"59 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The exciton-polariton, a quasi-particle formed by the coupling of excitons and photons, exhibits a semi-light-semi-matter nature, inheriting the advantages of both constituents and capable of achieving Bose-Einstein condensation at room temperature. This paper investigates the evolution of superposition states of semiconductor microcavity exciton-polariton Bose–Einstein condensate (BEC) within a ring-shaped structure. By employing theoretical modeling, the time-dependent dynamics of the superposition states of exciton-polaritons bound within a unique asymmetric ring-step potential well structure are analyzed, focusing on halide perovskite semiconductor materials. The study reveals correlations between the potential well structure of this step-like configuration and the transition of exciton-polariton BEC superposition states, shedding light on the evolution paths of BEC systems under specific structural influences and the fluctuation patterns of excitonic fields. These findings hold relevance for experimental manipulations of exciton-polariton superposition states within microcavities. This research demonstrates that ring-step potential well structures influence the excitation and evolution of exciton-polariton BEC superposition states, leading to transitions towards higher or lower order states. This transition is reflected macroscopically in alterations in the number and spatial distribution of interference petals in the superposition states. We consider initial states with orbital angular momentum quantum number l = 2, 3, 4, respectively. By exploiting the different structural relationships of ring-step potential wells, we achieve controlled evolutions of macroscopic occupation states, with interference petal numbers ranging from 4 to 6, 4–8, 6–8, 6–10, 8–10, 8–12, and 6–4.
{"title":"The dynamical evolution of exciton-polaritons in asymmetric ring-step potential well","authors":"Yifan Dong, Yuan Ren, Xiuqian Li, Zhenyu Xiong, Tieling Song, Aolin Guo, Longfei Guo, Baili Li, Peicheng Liu and Hao Wu","doi":"10.1088/1367-2630/ad692b","DOIUrl":"https://doi.org/10.1088/1367-2630/ad692b","url":null,"abstract":"The exciton-polariton, a quasi-particle formed by the coupling of excitons and photons, exhibits a semi-light-semi-matter nature, inheriting the advantages of both constituents and capable of achieving Bose-Einstein condensation at room temperature. This paper investigates the evolution of superposition states of semiconductor microcavity exciton-polariton Bose–Einstein condensate (BEC) within a ring-shaped structure. By employing theoretical modeling, the time-dependent dynamics of the superposition states of exciton-polaritons bound within a unique asymmetric ring-step potential well structure are analyzed, focusing on halide perovskite semiconductor materials. The study reveals correlations between the potential well structure of this step-like configuration and the transition of exciton-polariton BEC superposition states, shedding light on the evolution paths of BEC systems under specific structural influences and the fluctuation patterns of excitonic fields. These findings hold relevance for experimental manipulations of exciton-polariton superposition states within microcavities. This research demonstrates that ring-step potential well structures influence the excitation and evolution of exciton-polariton BEC superposition states, leading to transitions towards higher or lower order states. This transition is reflected macroscopically in alterations in the number and spatial distribution of interference petals in the superposition states. We consider initial states with orbital angular momentum quantum number l = 2, 3, 4, respectively. By exploiting the different structural relationships of ring-step potential wells, we achieve controlled evolutions of macroscopic occupation states, with interference petal numbers ranging from 4 to 6, 4–8, 6–8, 6–10, 8–10, 8–12, and 6–4.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"72 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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