A ratchet is a device that produces a net forward motion of an object from a periodic (or random) driving force. Although ratchets are common in watches and in cells (see Focus: Stalling a Molecular Motor), they are hard to make for quantum systems. Now researchers demonstrate a quantum ratchet for a collection of cold atoms trapped in an optical lattice [1]. By varying the lattice’s light fields in a time-dependent way, the researchers show that they canmove the atoms coherently from one lattice site to the next without disturbing the atoms’ quantum states.
{"title":"Quantum Ratchet Made Using an Optical Lattice","authors":"Michael Schirber","doi":"10.1103/physics.16.s140","DOIUrl":"https://doi.org/10.1103/physics.16.s140","url":null,"abstract":"A ratchet is a device that produces a net forward motion of an object from a periodic (or random) driving force. Although ratchets are common in watches and in cells (see Focus: Stalling a Molecular Motor), they are hard to make for quantum systems. Now researchers demonstrate a quantum ratchet for a collection of cold atoms trapped in an optical lattice [1]. By varying the lattice’s light fields in a time-dependent way, the researchers show that they canmove the atoms coherently from one lattice site to the next without disturbing the atoms’ quantum states.","PeriodicalId":20136,"journal":{"name":"Physics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135385368","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}
T hrow a ball into the air and the pull of Earth’s gravity will bring it crashing back down. But what about a ball of antimatter? Will it fall in the same way, or does it somehow experience gravity differently? Physicists have been exploring such questions for nearly a century but, until now, there had been no direct experimental test of antimatter in free fall. Releasing the results of observations of free-falling antihydrogen atoms, the Antihydrogen Laser Physics Apparatus (ALPHA) Collaboration at CERN in Switzerland shows that the particles experience the same gravitational pull as ordinary matter as they accelerate to Earth [1]. The collaboration says that the experiments are a landmark test of the weak
{"title":"Antimatter Feels Gravity Just like Matter","authors":"Allison Gasparini","doi":"10.1103/physics.16.167","DOIUrl":"https://doi.org/10.1103/physics.16.167","url":null,"abstract":"T hrow a ball into the air and the pull of Earth’s gravity will bring it crashing back down. But what about a ball of antimatter? Will it fall in the same way, or does it somehow experience gravity differently? Physicists have been exploring such questions for nearly a century but, until now, there had been no direct experimental test of antimatter in free fall. Releasing the results of observations of free-falling antihydrogen atoms, the Antihydrogen Laser Physics Apparatus (ALPHA) Collaboration at CERN in Switzerland shows that the particles experience the same gravitational pull as ordinary matter as they accelerate to Earth [1]. The collaboration says that the experiments are a landmark test of the weak","PeriodicalId":20136,"journal":{"name":"Physics","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135579628","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}
We consider the Casimir pressure between two metallic plates and calculate the four contributions to it determined by the propagating and evanescent waves and by the transverse magnetic and transverse electric polarizations of the electromagnetic field. The range of interplate separations is considered where nearly the whole pressure has its origin in the electromagnetic response of conduction electrons. In the Casimir physics, this response is described either by the dissipative Drude model resulting in contradictions with the measurement data or by the experimentally consistent but dissipationless plasma model. It is shown that the total transverse magnetic contribution to the Casimir pressure due to both the propagating and evanescent waves and the transverse electric contribution due to only the propagating waves, computed by means of the Drude model, correlate well with the corresponding results obtained using the plasma model. The conclusion is made that a disagreement between the theoretical predictions obtained using the Drude model and precision measurements of the Casimir force is not caused by the account of dissipation in itself, but arises from an incorrect description of the response of metals to the low-frequency transverse electric evanescent waves by this model. It is demonstrated that the Drude model has no supporting experimental evidence in the range of transverse electric evanescent waves, so that the above conclusion is consistent with all available information. The alternative test of the Drude model for the transverse electric evanescent waves suggested in the framework of classical electrodynamics is discussed.
{"title":"Casimir Effect Invalidates the Drude Model for Transverse Electric Evanescent Waves","authors":"Galina L. Klimchitskaya, Vladimir M. Mostepanenko","doi":"10.3390/physics5040062","DOIUrl":"https://doi.org/10.3390/physics5040062","url":null,"abstract":"We consider the Casimir pressure between two metallic plates and calculate the four contributions to it determined by the propagating and evanescent waves and by the transverse magnetic and transverse electric polarizations of the electromagnetic field. The range of interplate separations is considered where nearly the whole pressure has its origin in the electromagnetic response of conduction electrons. In the Casimir physics, this response is described either by the dissipative Drude model resulting in contradictions with the measurement data or by the experimentally consistent but dissipationless plasma model. It is shown that the total transverse magnetic contribution to the Casimir pressure due to both the propagating and evanescent waves and the transverse electric contribution due to only the propagating waves, computed by means of the Drude model, correlate well with the corresponding results obtained using the plasma model. The conclusion is made that a disagreement between the theoretical predictions obtained using the Drude model and precision measurements of the Casimir force is not caused by the account of dissipation in itself, but arises from an incorrect description of the response of metals to the low-frequency transverse electric evanescent waves by this model. It is demonstrated that the Drude model has no supporting experimental evidence in the range of transverse electric evanescent waves, so that the above conclusion is consistent with all available information. The alternative test of the Drude model for the transverse electric evanescent waves suggested in the framework of classical electrodynamics is discussed.","PeriodicalId":20136,"journal":{"name":"Physics","volume":"109 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135472274","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}
M aterials scientists have engineered systems in the laboratory that yield exotic particles not seen in nature. In particular, when electrons are confined to two dimensions, cooled to near absolute zero, and exposed to a strongmagnetic field, they capture part of this field and turn into weakly interacting particles called composite fermions (CFs). CFs display striking phenomena such as the fractional quantum Hall effect (FQHE). (See [1] for reviews of CFs, the
{"title":"In a Twist, Composite Fermions Form and Flow without a Magnetic Field","authors":"Jainendra Jain","doi":"10.1103/physics.16.163","DOIUrl":"https://doi.org/10.1103/physics.16.163","url":null,"abstract":"M aterials scientists have engineered systems in the laboratory that yield exotic particles not seen in nature. In particular, when electrons are confined to two dimensions, cooled to near absolute zero, and exposed to a strongmagnetic field, they capture part of this field and turn into weakly interacting particles called composite fermions (CFs). CFs display striking phenomena such as the fractional quantum Hall effect (FQHE). (See [1] for reviews of CFs, the","PeriodicalId":20136,"journal":{"name":"Physics","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135579474","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}
The combination of nuclear magnetic resonance with first-principles calculations uncovers the stacking patterns of layers of a quantum material—information that could enable a deeper understanding of the material’s behavior.
{"title":"A Fine Probe of Layer Stacking","authors":"Matteo Rini","doi":"10.1103/physics.16.s139","DOIUrl":"https://doi.org/10.1103/physics.16.s139","url":null,"abstract":"The combination of nuclear magnetic resonance with first-principles calculations uncovers the stacking patterns of layers of a quantum material—information that could enable a deeper understanding of the material’s behavior.","PeriodicalId":20136,"journal":{"name":"Physics","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135579634","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}
We analyze the correlations functions across the horizon in Hawking black hole radiation to reveal the correlations between Hawking particles and their partners. The effects of the underlying space–time on this are shown in various examples ranging from acoustic black holes to regular black holes.
{"title":"The Hawking Effect in the Particles–Partners Correlations","authors":"Roberto Balbinot, Alessandro Fabbri","doi":"10.3390/physics5040063","DOIUrl":"https://doi.org/10.3390/physics5040063","url":null,"abstract":"We analyze the correlations functions across the horizon in Hawking black hole radiation to reveal the correlations between Hawking particles and their partners. The effects of the underlying space–time on this are shown in various examples ranging from acoustic black holes to regular black holes.","PeriodicalId":20136,"journal":{"name":"Physics","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135580010","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}
{"title":"Breakthrough Prize for Quantum Field Theorists","authors":"Michael Schirber","doi":"10.1103/physics.16.165","DOIUrl":"https://doi.org/10.1103/physics.16.165","url":null,"abstract":"","PeriodicalId":20136,"journal":{"name":"Physics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135719267","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}
W hen amobile impurity such as an electron interacts with a bath of bosons, it forms a quasiparticle—a polaron—whose properties are very different from those of the impurity itself. For example, in a superconductor, electron–phonon interactions generate polarons that attract one another (forming Cooper pairs) even though individual electrons are mutually repulsive. A general understanding of what dictates polarons’ properties and their resulting interactions remains elusive but is fundamental for finding ways to tune andmanipulate these quasiparticles. Addressing this problemwith experiments and theory, Li Bing Tan of the Swiss Federal Institute of Technology (ETH) in Zurich and her colleagues demonstrate a mechanism for modifying impurity interactions in a bosonic bath [1]. By changing the bath density, they turn repulsive interactions into attractive ones.
{"title":"Quasiparticles Repel, Then Attract","authors":"Rachel Berkowitz","doi":"10.1103/physics.16.s132","DOIUrl":"https://doi.org/10.1103/physics.16.s132","url":null,"abstract":"W hen amobile impurity such as an electron interacts with a bath of bosons, it forms a quasiparticle—a polaron—whose properties are very different from those of the impurity itself. For example, in a superconductor, electron–phonon interactions generate polarons that attract one another (forming Cooper pairs) even though individual electrons are mutually repulsive. A general understanding of what dictates polarons’ properties and their resulting interactions remains elusive but is fundamental for finding ways to tune andmanipulate these quasiparticles. Addressing this problemwith experiments and theory, Li Bing Tan of the Swiss Federal Institute of Technology (ETH) in Zurich and her colleagues demonstrate a mechanism for modifying impurity interactions in a bosonic bath [1]. By changing the bath density, they turn repulsive interactions into attractive ones.","PeriodicalId":20136,"journal":{"name":"Physics","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135719266","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}
B lack holes are astonishing objects that can pack the mass of Earth into a space the size of a pea. A remarkable attribute is their stunning simplicity, which is encapsulated in the celebrated uniqueness theorems [1]. Briefly stated, these theorems say that there is only one solution to Einstein’s equations of general relativity for a fully collapsed (nonevolving) system having fixed mass and angular momentum [2]. The implication is that all black holes that have settled down to equilibriumwith the samemass and rotation are precisely the same: their entire behavior described by a single equation—the so-called Kerr solution—filling only a few lines of paper!
{"title":"Two Black Holes Masquerading as One","authors":"Toby Wiseman","doi":"10.1103/physics.16.164","DOIUrl":"https://doi.org/10.1103/physics.16.164","url":null,"abstract":"B lack holes are astonishing objects that can pack the mass of Earth into a space the size of a pea. A remarkable attribute is their stunning simplicity, which is encapsulated in the celebrated uniqueness theorems [1]. Briefly stated, these theorems say that there is only one solution to Einstein’s equations of general relativity for a fully collapsed (nonevolving) system having fixed mass and angular momentum [2]. The implication is that all black holes that have settled down to equilibriumwith the samemass and rotation are precisely the same: their entire behavior described by a single equation—the so-called Kerr solution—filling only a few lines of paper!","PeriodicalId":20136,"journal":{"name":"Physics","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135866074","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}
Using a metallic grating and infrared light, researchers have uncovered a light–matter coupling regime where the local coupling strength can be 3.5 times higher than the global average for the material.
{"title":"Metallic Gratings Produce a Strong Surprise","authors":"Katherine Wright","doi":"10.1103/physics.16.s130","DOIUrl":"https://doi.org/10.1103/physics.16.s130","url":null,"abstract":"Using a metallic grating and infrared light, researchers have uncovered a light–matter coupling regime where the local coupling strength can be 3.5 times higher than the global average for the material.","PeriodicalId":20136,"journal":{"name":"Physics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136099744","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：