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Articles 1 - 23 of 23
Full-Text Articles in Physics
Interaction-Free Effects Between Distant Atoms, Yakir Aharonov, Eliahu Cohen, Avshalom C. Elitzur, Lee Smolin
Interaction-Free Effects Between Distant Atoms, Yakir Aharonov, Eliahu Cohen, Avshalom C. Elitzur, Lee Smolin
Mathematics, Physics, and Computer Science Faculty Articles and Research
A Gedanken experiment is presented where an excited and a ground-state atom are positioned such that, within the former’s half-life time, they exchange a photonwith 50% probability.Ameasurement of their energy statewill therefore indicate in 50% of the cases that no photon was exchanged. Yet other measurements would reveal that, by the mere possibility of exchange, the two atoms have become entangled. Consequently, the “no exchange” result, apparently precluding entanglement, is non-locally established between the atoms by this very entanglement. This quantum-mechanical version of the ancient Liar Paradox can be realized with already existing transmission schemes, with the addition of Bell’s …
Past Observable Dynamics Of A Continuously Monitored Qubit, Luis Pedro García-Pinto, Justin Dressel
Past Observable Dynamics Of A Continuously Monitored Qubit, Luis Pedro García-Pinto, Justin Dressel
Mathematics, Physics, and Computer Science Faculty Articles and Research
Monitoring a quantum observable continuously in time produces a stochastic measurement record that noisily tracks the observable. For a classical process, such noise may be reduced to recover an average signal by minimizing the mean squared error between the noisy record and a smooth dynamical estimate. We show that for a monitored qubit, this usual procedure returns unusual results. While the record seems centered on the expectation value of the observable during causal generation, examining the collected past record reveals that it better approximates a moving-mean Gaussian stochastic process centered at a distinct (smoothed) observable estimate. We show that this …
Arrow Of Time For Continuous Quantum Measurement, Justin Dressel, Areeya Chantasri, Andrew N. Jordan, Alexander N. Korotkov
Arrow Of Time For Continuous Quantum Measurement, Justin Dressel, Areeya Chantasri, Andrew N. Jordan, Alexander N. Korotkov
Mathematics, Physics, and Computer Science Faculty Articles and Research
We investigate the statistical arrow of time for a quantum system being monitored by a sequence of measurements. For a continuous qubit measurement example, we demonstrate that time-reversed evolution is always physically possible, provided that the measurement record is also negated. Despite this restoration of dynamical reversibility, a statistical arrow of time emerges, and may be quantified by the log-likelihood difference between forward and backward propagation hypotheses. We then show that such reversibility is a universal feature of nonprojective measurements, with forward or backward Janus measurement sequences that are time-reversed inverses of each other.
Weak-Value Amplification And Optimal Parameter Estimation In The Presence Of Correlated Noise, Josiah Sinclair, Matin Hallaji, Aephraim M. Steinberg, Jeff Tollaksen, Andrew N. Jordan
Weak-Value Amplification And Optimal Parameter Estimation In The Presence Of Correlated Noise, Josiah Sinclair, Matin Hallaji, Aephraim M. Steinberg, Jeff Tollaksen, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
We analytically and numerically investigate the performance of weak-value amplification (WVA) and related parameter estimation methods in the presence of temporally correlated noise. WVA is a special instance of a general measurement strategy that involves sorting data into separate subsets based on the outcome of a second “partitioning” measurement. Using a simplified correlated noise model that can be analyzed exactly together with optimal statistical estimators, we compare WVA to a conventional measurement method. We find that WVA indeed yields a much lower variance of the parameter of interest than the conventional technique does, optimized in the absence of any partitioning …
Evolution Of Superoscillations For Schrödinger Equation In A Uniform Magnetic Field, Fabrizio Colombo, Jonathan Gantner, Daniele C. Struppa
Evolution Of Superoscillations For Schrödinger Equation In A Uniform Magnetic Field, Fabrizio Colombo, Jonathan Gantner, Daniele C. Struppa
Mathematics, Physics, and Computer Science Faculty Articles and Research
Aharonov-Berry superoscillations are band-limited functions that oscillate faster than their fastest Fourier component. Superoscillations appear in several fields of science and technology, such as Aharonov’s weak measurement in quantum mechanics, in optics, and in signal processing. An important issue is the study of the evolution of superoscillations using the Schrödinger equation when the initial datum is a weak value. Some superoscillatory functions are not square integrable, but they are real analytic functions that can be extended to entire holomorphic functions. This fact leads to the study of the continuity of a class of convolution operators acting on suitable spaces of …
Sheaf Theoretic Formulation For Consciousness And Qualia And Relationship To The Idealism Of Non-Dual Philosophies, Menas Kafatos, Goro Kato
Sheaf Theoretic Formulation For Consciousness And Qualia And Relationship To The Idealism Of Non-Dual Philosophies, Menas Kafatos, Goro Kato
Mathematics, Physics, and Computer Science Faculty Articles and Research
Questions about the nature of reality, whether Consciousness is the fundamental reality in the universe, and what is Consciousness itself, have no answer in systems that assume an external reality independent of Consciousness. Ultimately, the ontological foundation of such systems is the absolute division of subject and object. We advocate instead what we consider to be an approach that is in agreement with the foundation of quantum reality, which is based on Rāmānuja’s version of Vedanta philosophy and non-dual Kashmir Śaivism. Quantum mechanics opened the door to consciousness, but it cannot account for consciousness. However, the quantum measurement problem implies …
Linear Feedback Stabilization Of A Dispersively Monitored Qubit, Taylor Lee Patti, Areeya Chantasri, Luis Pedro García-Pintos, Andrew N. Jordan, Justin Dressel
Linear Feedback Stabilization Of A Dispersively Monitored Qubit, Taylor Lee Patti, Areeya Chantasri, Luis Pedro García-Pintos, Andrew N. Jordan, Justin Dressel
Mathematics, Physics, and Computer Science Faculty Articles and Research
The state of a continuously monitored qubit evolves stochastically, exhibiting competition between coherent Hamiltonian dynamics and diffusive partial collapse dynamics that follow the measurement record. We couple these distinct types of dynamics together by linearly feeding the collected record for dispersive energy measurements directly back into a coherent Rabi drive amplitude. Such feedback turns the competition cooperative and effectively stabilizes the qubit state near a target state. We derive the conditions for obtaining such dispersive state stabilization and verify the stabilization conditions numerically.We include common experimental nonidealities, such as energy decay, environmental dephasing, detector efficiency, and feedback delay, and show …
Is Qbism The Future Of Quantum Physics?, Kelvin J. Mcqueen
Is Qbism The Future Of Quantum Physics?, Kelvin J. Mcqueen
Philosophy Faculty Articles and Research
A review of Hans Christian von Baeyer’s QBism: The Future of Quantum Physics.
Ultrasensitive Inverse Weak-Value Tilt Meter, Julián Martínez-Rincón, Christopher A. Mullarkey, Gerardo I. Viza, Wei-Tao Liu, John C. Howell
Ultrasensitive Inverse Weak-Value Tilt Meter, Julián Martínez-Rincón, Christopher A. Mullarkey, Gerardo I. Viza, Wei-Tao Liu, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We present an interferometric technique for measuring ultrasmall tilts. The information of a tilt in one of the mirrors of a modified Sagnac interferometer is carried by the phase difference between the counter-propagating laser beams. Using a small misalignment of the interferometer, orthogonal to the plane of the tilt, a bimodal (or two-fringe) pattern is induced in the beam’s transverse power distribution. By tracking the mean of such a distribution, using a split detector, a sensitive measurement of the phase is performed. With 1.2 mW of continuous-wave laser power, the technique has a shot noise limited sensitivity of 56 frad/Hz−−−√ …
Is A Time Symmetric Interpretation Of Quantum Theory Possible Without Retrocausality?, Matthew S. Leifer, Matthew F. Pusey
Is A Time Symmetric Interpretation Of Quantum Theory Possible Without Retrocausality?, Matthew S. Leifer, Matthew F. Pusey
Mathematics, Physics, and Computer Science Faculty Articles and Research
Huw Price has proposed an argument that suggests a time symmetric ontology for quantum theory must necessarily be retrocausal, i.e. it must involve influences that travel backwards in time. One of Price's assumptions is that the quantum state is a state of reality. However, one of the reasons for exploring retrocausality is that it offers the potential for evading the consequences of no-go theorems, including recent proofs of the reality of the quantum state. Here, we show that this assumption can be replaced by a different assumption, called λ-mediation, that plausibly holds independently of the status of the quantum …
Practical Advantages Of Almost-Balanced-Weak-Value Metrological Techniques, Julián Martínez-Rincón, Zekai Chen, John C. Howell
Practical Advantages Of Almost-Balanced-Weak-Value Metrological Techniques, Julián Martínez-Rincón, Zekai Chen, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
Precision measurements of ultrasmall linear velocities of one of the mirrors in a Michelson interferometer are performed using two different weak-value techniques. We show that the technique of almost-balanced weak values (ABWV) offers practical advantages over the technique of weak-value amplification, resulting in larger signal-to-noise ratios and the possibility of longer integration times due to robustness to slow drifts. As an example of the performance of the ABWV protocol we report a velocity sensitivity of 60 fm/s after 40 h of integration time. The sensitivity of the Doppler shift due to the moving mirror is 150 nHz.
Beurling-Lax Type Theorems In The Complex And Quaternionic Setting, Daniel Alpay, Irene Sabadini
Beurling-Lax Type Theorems In The Complex And Quaternionic Setting, Daniel Alpay, Irene Sabadini
Mathematics, Physics, and Computer Science Faculty Articles and Research
We give a generalization of the Beurling–Lax theorem both in the complex and quaternionic settings. We consider in the first case functions meromorphic in the right complex half-plane, and functions slice hypermeromorphic in the right quaternionic half-space in the second case. In both settings we also discuss a unified framework, which includes both the disk and the half-plane for the complex case and the open unit ball and the half-space in the quaternionic setting.
The Case Of The Disappearing (And Re-Appearing) Particle, Yakir Aharonov, Eliahu Cohen, Ariel Landau, Avshalom C. Elitzur
The Case Of The Disappearing (And Re-Appearing) Particle, Yakir Aharonov, Eliahu Cohen, Ariel Landau, Avshalom C. Elitzur
Mathematics, Physics, and Computer Science Faculty Articles and Research
A novel prediction is derived by the Two-State-Vector-Formalism (TSVF) for a particle superposed over three boxes. Under appropriate pre- and post-selections, and with tunneling enabled between two of the boxes, it is possible to derive not only one, but three predictions for three different times within the intermediate interval. These predictions are moreover contradictory. The particle (when looked for using a projective measurement) seems to disappear from the first box where it would have been previously found with certainty, appearing instead within the third box, to which no tunneling is possible, and later re-appearing within the second. It turns out …
The Two-Time Interpretation And Macroscopic Time-Reversibility, Yakir Aharonov, Eliahu Cohen, Tomer Landsberger
The Two-Time Interpretation And Macroscopic Time-Reversibility, Yakir Aharonov, Eliahu Cohen, Tomer Landsberger
Mathematics, Physics, and Computer Science Faculty Articles and Research
The two-state vector formalism motivates a time-symmetric interpretation of quantum mechanics that entails a resolution of the measurement problem. We revisit a post-selection-assisted collapse model previously suggested by us, claiming that unlike the thermodynamic arrow of time, it can lead to reversible dynamics at the macroscopic level. In addition, the proposed scheme enables us to characterize the classical-quantum boundary. We discuss the limitations of this approach and its broad implications for other areas of physics.
On A Class Of Quaternionic Positive Definite Functions And Their Derivatives, Daniel Alpay, Fabrizio Colombo, Irene Sabadini
On A Class Of Quaternionic Positive Definite Functions And Their Derivatives, Daniel Alpay, Fabrizio Colombo, Irene Sabadini
Mathematics, Physics, and Computer Science Faculty Articles and Research
In this paper, we start the study of stochastic processes over the skew field of quaternions. We discuss the relation between positive definite functions and the covariance of centered Gaussian processes and the construction of stochastic processes and their derivatives. The use of perfect spaces and strong algebras and the notion of Fock space are crucial in this framework.
Slow Light In Flight Imaging, Kali Wilson, Bethany Little, Genevieve Gariepy, Robert Henderson, John C. Howell, Daniele Faccio
Slow Light In Flight Imaging, Kali Wilson, Bethany Little, Genevieve Gariepy, Robert Henderson, John C. Howell, Daniele Faccio
Mathematics, Physics, and Computer Science Faculty Articles and Research
Slow-light media are of interest in the context of quantum computing and enhanced measurement of quantum effects, with particular emphasis on using slow light with single photons. We use light-in-flight imaging with a single-photon avalanche diode camera array to image in situ pulse propagation through a slow-light medium consisting of heated rubidium vapor. Light-in-flight imaging of slow-light propagation enables direct visualization of a series of physical effects, including simultaneous observation of spatial pulse compression and temporal pulse dispersion. Additionally, the single-photon nature of the camera allows for observation of the group velocity of single photons with measured single-photon fractional delays …
Rapid Estimation Of Drifting Parameters In Continuously Measured Quantum Systems, Luis Cortez, Areeya Chantasri, Luis Pedro García-Pintos, Justin Dressel, Andrew N. Jordan
Rapid Estimation Of Drifting Parameters In Continuously Measured Quantum Systems, Luis Cortez, Areeya Chantasri, Luis Pedro García-Pintos, Justin Dressel, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
We investigate the determination of a Hamiltonian parameter in a quantum system undergoing continuous measurement. We demonstrate a computationally rapid method to estimate an unknown and possibly timedependent parameter, where we maximize the likelihood of the observed stochastic readout. By dealing directly with the raw measurement record rather than the quantum-state trajectories, the estimation can be performed while the data are being acquired, permitting continuous tracking of the parameter during slow drifts in real time. Furthermore, we incorporate realistic nonidealities, such as decoherence processes and measurement inefficiency. As an example, we focus on estimating the value of the Rabi frequency …
Experimental Demonstration Of Direct Path State Characterization By Strongly Measuring Weak Values In A Matter-Wave Interferometer, Tobias Denkmayr, Hermann Geppert, Hartmut Lemmel, Mordecai Waegell, Justin Dressel, Yuji Hasegawa, Stephan Sponar
Experimental Demonstration Of Direct Path State Characterization By Strongly Measuring Weak Values In A Matter-Wave Interferometer, Tobias Denkmayr, Hermann Geppert, Hartmut Lemmel, Mordecai Waegell, Justin Dressel, Yuji Hasegawa, Stephan Sponar
Mathematics, Physics, and Computer Science Faculty Articles and Research
A method was recently proposed and experimentally realized for characterizing a quantum state by directly measuring its complex probability amplitudes in a particular basis using so-called weak values. Recently, Vallone and Dequal [Phys. Rev. Lett. 116, 040502 (2016)] showed theoretically that weak measurements are not a necessary condition to determine the weak value. Here, we report a measurement scheme used in a matter-wave interferometric experiment in which the neutron path system’s quantum state was characterized via direct measurements, using both strong and weak interactions. Experimental evidence is given that strong interactions outperform weak ones for tomographic accuracy. Our results are …
Saving The Physics Ii: Who Needs To Be Saved? It Depends On Your Metaphysics, Menas Kafatos
Saving The Physics Ii: Who Needs To Be Saved? It Depends On Your Metaphysics, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Physics does not need to be saved. If anything, physics was rescued in the early twentieth century with the advancement of both the theories of relativity and quantum mechanics. What needs to be saved is our world outlook or metaphysics because how a society acts and develops depends on what its belief systems are. Here we explore how a new metaphysics where consciousness is fundamental might just be what modern societies need.
Gamifying Quantum Theory, Matthew S. Leifer
Gamifying Quantum Theory, Matthew S. Leifer
Mathematics, Physics, and Computer Science Faculty Articles and Research
"Over the past few years, the trend of gamification has gradually seeped into quantum research, education and outreach, so that we now have a critical mass of games based on quantum mechanics. I thought the time was right to discuss quantum gamification at the APS March meeting[.]"
Janus Sequences Of Quantum Measurements And The Arrow Of Time, Andrew N. Jordan, Areeya Chantasri, Kater Murch, Justin Dressel, Alexander N. Korotkov
Janus Sequences Of Quantum Measurements And The Arrow Of Time, Andrew N. Jordan, Areeya Chantasri, Kater Murch, Justin Dressel, Alexander N. Korotkov
Mathematics, Physics, and Computer Science Faculty Articles and Research
We examine the time reversal symmetry of quantum measurement sequences by introducing a forward and backward Janus sequence of measurements. If the forward sequence of measurements creates a sequence of quantum states in time, starting from an initial state and ending in a final state, then the backward sequence begins with the time-reversed final state, exactly retraces the intermediate states, and ends with the time-reversed initial state. We prove that such a sequence can always be constructed, showing that unless the measurements are ideal projections, it is impossible to tell if a given sequence of measurements is progressing forward or …
Is A Time Symmetric Interpretation Of Quantum Theory Possible Without Retrocausality?, Matthew S. Leifer, Matthew F. Pusey
Is A Time Symmetric Interpretation Of Quantum Theory Possible Without Retrocausality?, Matthew S. Leifer, Matthew F. Pusey
Mathematics, Physics, and Computer Science Faculty Articles and Research
Huw Price has proposed an argument that suggests a time-symmetric ontology for quantum theory must necessarily be retrocausal, i.e. it must involve influences that travel backwards in time. One of Price's assumptions is that the quantum state is a state of reality. However, one of the reasons for exploring retrocausality is that it offers the potential for evading the consequences of no-go theorems, including recent proofs of the reality of the quantum state. Here, we show that this assumption can be replaced by a different assumption, called λ-mediation, that plausibly holds independently of the status of the quantum state. We …
Review Of Qbism: The Future Of Quantum Physics, Matthew S. Leifer
Review Of Qbism: The Future Of Quantum Physics, Matthew S. Leifer
Mathematics, Physics, and Computer Science Faculty Articles and Research
A review of QBism: The Future of Quantum Physics by Hans Christian von Baeyer.