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Articles 1 - 30 of 235
Full-Text Articles in Quantum Physics
Glassy Magnetic Freezing Of Interacting Clusters In Materials Related To The Lk-99 Family, Serafim Teknowijoyo, Domenico Napoletani, Vahan Nikoghosyan, Armen Gulian
Glassy Magnetic Freezing Of Interacting Clusters In Materials Related To The Lk-99 Family, Serafim Teknowijoyo, Domenico Napoletani, Vahan Nikoghosyan, Armen Gulian
Mathematics, Physics, and Computer Science Faculty Articles and Research
We report reproducible magnetization anomalies appearing below room temperature in copper-doped apatite materials belonging to the LK-99 family synthesized via hydrothermal methods. These anomalies are observed consistently across samples prepared under comparable conditions. Although the extracted Mydosh parameter lies within the range often associated with vortex-glass behavior in superconductors, a detailed analysis of DC magnetization, AC susceptibility, field dependence, and magnetic memory effects demonstrates that the observed phenomena are not related to superconductivity. Instead, the data are consistent with glassy magnetic freezing of interacting clusters. Compositional and structural analysis identifies covellite (CuS), one of the constituent phases in these multiphase …
Capturing An Electron In The Virtual State, Alok Nath Singh, Bibek Bhandari, Rafael Sánchez, Andrew N. Jordan
Capturing An Electron In The Virtual State, Alok Nath Singh, Bibek Bhandari, Rafael Sánchez, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
We address a foundational question in quantum mechanics: can a particle be directly found in a classically-forbidden virtual state? We instantiate this conceptual question by investigating the traversal of electrons through a tunnel barrier, which we define in a triple quantum dot system where the occupation of the central dot is energetically avoided. The motivation behind this setup is to answer whether the central dot is occupied or not during a virtual transition when it is being explicitly monitored. We investigate this problem in two different limits of continuous measurements: the stochastic quantum diffusion and the quantum jump. We find …
Classical-Correlation-Enhanced Weak-Value Amplification Resilient To Persistent Noises, Xu-Song Hong, Gong-Chu Li, Lei Chen, Si-Qi Zhang, Hua-Qin Xu, Yuancheng Liu, Shengshi Pang, Andrew N. Jordan, Geng Chen, Chuan-Feng Li, Guang-Can Guo
Classical-Correlation-Enhanced Weak-Value Amplification Resilient To Persistent Noises, Xu-Song Hong, Gong-Chu Li, Lei Chen, Si-Qi Zhang, Hua-Qin Xu, Yuancheng Liu, Shengshi Pang, Andrew N. Jordan, Geng Chen, Chuan-Feng Li, Guang-Can Guo
Mathematics, Physics, and Computer Science Faculty Articles and Research
Weak measurement (WM) offers the advantage of amplifying small signals at the cost of postselecting a small portion of the probes. This so-called weak-value amplification effect makes it compare favorably with conventional techniques (without postselection) to overcome various technical noises. However, certain types of technical noise, such as jitter and pixelation, present insurmountable limitations for both WM and conventional techniques. In this work, we propose an advanced variant of WM that incorporates time-momentum correlation (TMC) into biased weak measurement (BWM). By employing the Fisher information metric, we theoretically show that TMC-BWM can overcome jitter and pixelation, and meanwhile extract significantly …
What Do Black Holes Teach Us About Wigner’S Friend?, Emily Adlam
What Do Black Holes Teach Us About Wigner’S Friend?, Emily Adlam
Mathematics, Physics, and Computer Science Faculty Articles and Research
Recently, Hausmann and Renner have pointed out that several famous paradoxes relating to black holes have a similar character to various Extended Wigner’s Friend paradoxes. In this paper I consider what the connection between these things could teach us about the Wigner’s Friend scenarios. I argue that if we take the analogy between these cases seriously, the black hole paradoxes appear to favour a certain class of response to the Wigner’s Friend scenario - specifically, those which posit intrinsic relationality, rather than effective and emergent relationality, and also those which posit some kind of retrocausality.
Describing The Wave Function Collapse Process With A State-Dependent Hamiltonian, Le Hu, Andrew N. Jordan
Describing The Wave Function Collapse Process With A State-Dependent Hamiltonian, Le Hu, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
Quantum mechanics admits two distinct evolutions: deterministic unitary dynamics governed by the Schrödinger equation and the probabilistic collapse of the wave function. We show that the continuous collapse of a quantum state under measurement can, on a trajectory-by-trajectory basis, be equivalently described as unitary evolution generated by a time- and state-dependent Hermitian Hamiltonian with stochastic parameters. While the ensemble dynamics remains non-unitary, each individual trajectory thus admits a unitary representation. We derive explicit forms of such Hamiltonians for projective measurements on arbitrary n-level systems and for continuous position measurements of a harmonic oscillator, and we propose experimental schemes to …
Quantum Indiscernibility And Perspectivalism, Emily Adlam
Quantum Indiscernibility And Perspectivalism, Emily Adlam
Mathematics, Physics, and Computer Science Faculty Articles and Research
It has often been suggested that similar quantum particles may be a counterexample to the principle of the Identity of Indiscernibles. In this article, I discuss the status of indiscernibility in a perspectival approach to quantum mechanics. I argue that adopting an internal physical perspective can have the effect of making entities discernible even if they are not discernible relative to external reference frames, and thus perspectivalism offers a new way to understand the physical meaning of weak discernibility. I discuss whether this approach is circular, and I consider whether the reference frames involved are physically meaningful. I conclude that …
Cdj-Pontryagin Optimal Control For General Continuously Monitored Quantum Systems, Tathagata Karmakar, Andrew N. Jordan
Cdj-Pontryagin Optimal Control For General Continuously Monitored Quantum Systems, Tathagata Karmakar, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
The Chantasri-Dressel-Jordan (CDJ) stochastic path integral formalism (Chantasri et al. 2013 and 2015) characterizes the statistics of the readouts and the most likely conditional evolution of continuously monitored quantum systems involving a few qubits or quantum harmonic oscillators in Gaussian states. In our work, we generalize the CDJ formalism to arbitrary continuously monitored systems by introducing a costate operator. We then prescribe a generalized Pontryagin's maximum principle for quantum systems undergoing arbitrary evolution and find conditions on optimal control protocols. We show that the CDJ formalism's most likely path can be cast as a quantum Pontryagin's maximum principle, where the …
Making The Virtual Real: Measurement-Powered Tunneling Engines, Rafael Sánchez, Alok Nath Singh, Andrew N. Jordan, Bibek Bhandari
Making The Virtual Real: Measurement-Powered Tunneling Engines, Rafael Sánchez, Alok Nath Singh, Andrew N. Jordan, Bibek Bhandari
Mathematics, Physics, and Computer Science Faculty Articles and Research
Quantum tunneling allows electrons to be transferred between two regions separated by an energetically forbidden barrier. Performing a position measurement that finds a particle in the barrier forces the tunneling electrons to transition from having a classically forbidden energy to an energy above the barrier height. We exploit this effect to define quantum tunneling engines that can use the unconditioned detection of virtually occupied states as a resource for power generation and cooling. Leveraging energy exchange with the detector, we show that the device can operate in a hybrid regime, enabling simultaneous cooling and power generation. Furthermore, we demonstrate measurement-assisted …
Charge Acceleration Without Radiation, Yakir Aharonov, D. Collins, S. Popescu
Charge Acceleration Without Radiation, Yakir Aharonov, D. Collins, S. Popescu
Mathematics, Physics, and Computer Science Faculty Articles and Research
The existence of electromagnetic radiation—radio waves, microwaves, light, X-rays, and so on—is one of the most important physical phenomena, and our ability to manipulate them is one of the most significant technological achievement of humankind. Underlying this ability is our understanding of how radiation is produced: Whenever an electric charge is accelerated, it radiates. Or, at least, this is how it has been hitherto universally thought. Here, we prove that quantum mechanically electric charges can be accelerated without radiating. The physical setup leading to this behavior is relatively simple (once one knows what to do), but its reasons are deep: …
Quantum Benchmarking Of High-Fidelity Noise-Biased Operations On A Detuned Kerr-Cat Qubit, Bingcheng Qing, Ahmed Hajr, Ke Wang, Gerwin Koolstra, Long B. Nguyen, Jordan Hines, Irwin Huang, Bibek Bhandari, Larry Chen, Ziqi Kang, Christian Jünger, Noah Goss, Nikitha Jain, Hyunseong Kim, Kan-Heng Lee, Akel Hashim, Nicholas E. Frattini, Zahra Pedramrazi, Justin Dressel, Andrew N. Jordan, David I. Santiago, Irfan Siddiqi
Quantum Benchmarking Of High-Fidelity Noise-Biased Operations On A Detuned Kerr-Cat Qubit, Bingcheng Qing, Ahmed Hajr, Ke Wang, Gerwin Koolstra, Long B. Nguyen, Jordan Hines, Irwin Huang, Bibek Bhandari, Larry Chen, Ziqi Kang, Christian Jünger, Noah Goss, Nikitha Jain, Hyunseong Kim, Kan-Heng Lee, Akel Hashim, Nicholas E. Frattini, Zahra Pedramrazi, Justin Dressel, Andrew N. Jordan, David I. Santiago, Irfan Siddiqi
Mathematics, Physics, and Computer Science Faculty Articles and Research
Ubiquitous noise sources in quantum systems remain a key obstacle to building quantum computers, necessitating the use of quantum error correction codes. Recently, error-correcting codes tailored for noise-biased systems have been shown to offer high fault-tolerance thresholds and reduced hardware overhead, positioning noisebiased qubits as promising candidates for building universal quantum computers. However, quantum operations on these platforms remain challenging, and their noise structures have not yet been rigorously benchmarked to the same extent as those of conventional quantum hardware. In this work, we develop a comprehensive quantum control toolbox for a scalable noise-biased qubit, detuned Kerr-cat qubit, including initialization, …
Revealing The Fuel Of A Quantum Continuous Measurement-Based Refrigerator, Cyril Elouard, Sreenath K. Manikandan, Andrew N. Jordan, Géraldine Haack
Revealing The Fuel Of A Quantum Continuous Measurement-Based Refrigerator, Cyril Elouard, Sreenath K. Manikandan, Andrew N. Jordan, Géraldine Haack
Mathematics, Physics, and Computer Science Faculty Articles and Research
While quantum measurements have been shown to constitute a resource for operating quantum thermal machines, the nature of the energy exchanges involved in the interaction between system and measuring apparatus is still under debate. In this work, we show that a microscopic model of the apparatus is necessary to unambiguously determine whether quantum measurements provide energy in the form of heat or work. We illustrate this result by considering a measurement-based refrigerator, made of a double quantum dot embedded in a two-terminal device, with the charge of one of the dots being continuously monitored. Tuning the parameters of the measurement …
Gpu-Accelerated Effective Hamiltonian Calculator, Abhishek Chakraborty, Taylor L. Patti, Brucek Khailany, Andrew N. Jordan, Anima Anandkumar
Gpu-Accelerated Effective Hamiltonian Calculator, Abhishek Chakraborty, Taylor L. Patti, Brucek Khailany, Andrew N. Jordan, Anima Anandkumar
Mathematics, Physics, and Computer Science Faculty Articles and Research
Effective Hamiltonian calculations for large quantum systems can be both analytically intractable and numerically expensive using standard techniques. In this manuscript, we present numerical techniques inspired by Nonperturbative Analytical Diagonalization (NPAD) and the Magnus expansion for the efficient calculation of effective Hamiltonians. While these tools are appropriate for a wide array of applications, we here demonstrate their utility for models that can be realized in circuit-QED settings. Our numerical techniques are available as an opensource Python package, qCHeff, which is available on GitHub (https://github.com/ NVlabs/qCHeff) and PyPI (https://pypi.org/ project/qcheff/). We use the CuPy library for GPU-acceleration …
Modeling-Based Prediction Of Current Oscillation With The Josephson Frequency In Voltage-Biased Phase-Slip Center Filaments, Armen Gulian
Modeling-Based Prediction Of Current Oscillation With The Josephson Frequency In Voltage-Biased Phase-Slip Center Filaments, Armen Gulian
Mathematics, Physics, and Computer Science Faculty Articles and Research
In this article, we demonstrate that the voltage-biased phase-slip center (PSC) can act as a direct equivalent (not merely an analogy) of the Josephson effect in Josephson junctions (JJs). We analyze the behavior of PSCs in the case when a constant voltage V is applied to the superconducting filament. The analysis is performed using finite element modeling on the basis of time-dependent Ginzburg–Landau (TDGL) equations. It reveals that the current in the filament oscillates with the Josephson frequency ω = 2eV/h. This fact may have important corollaries in practice.
Symmetrically Threaded Superconducting Quantum Interference Devices As Next-Generation Kerr-Cat Qubits, Bibek Bhandari, Irwin Huang, Ahmed Hajr, Kagan Yanik, Bingcheng Qing, Ke Wang, David I. Santiago, Justin Dressel, Irfan Siddiqi, Andrew N. Jordan
Symmetrically Threaded Superconducting Quantum Interference Devices As Next-Generation Kerr-Cat Qubits, Bibek Bhandari, Irwin Huang, Ahmed Hajr, Kagan Yanik, Bingcheng Qing, Ke Wang, David I. Santiago, Justin Dressel, Irfan Siddiqi, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
Kerr-cat qubits are bosonic qubits offering autonomous bit-flip protection, traditionally studied using driven superconducting nonlinear asymmetric inductive element (SNAIL) oscillators. Here, we theoretically explore an alternative circuit for Kerr-cat qubits based on symmetrically threaded superconducting quantum interference devices (SQUIDs). The symmetrically threaded SQUID (STS) architecture employs a simplified flux-pumped design that suppresses two-photon dissipation, a dominant loss mechanism in high-Kerr regimes, by engineering the drive Hamiltonian’s flux operator to generate only even-order harmonics. By fulfilling two critical criteria for practical Kerr-cat qubit operation, the STS emerges as an ideal platform: (1) a static Hamiltonian with diluted Kerr nonlinearity (achieved via …
Relational Observables, Quiddities, And Structural Realism, Emily Adlam
Relational Observables, Quiddities, And Structural Realism, Emily Adlam
Mathematics, Physics, and Computer Science Faculty Articles and Research
In this article, I argue that modern spacetime physics causes problems for a number of traditional accounts of modality, but also offers important new ideas about the connection between modal and non-modal features of reality. I suggest that recent work on relational observables in general relativity and quantum gravity can help us understand how non-modal features of reality could arise from modal features of reality within some form of modal ontic structural realism. In particular, I argue that the notion of an ‘internal view,’ as employed in the partial/complete observables formalism and the quantum reference frame formalism, is an important …
Analyticity And Supershift With Regular Sampling, Fabrizio Colombo, Irene Sabadini, Daniele C. Struppa, Alain Yger
Analyticity And Supershift With Regular Sampling, Fabrizio Colombo, Irene Sabadini, Daniele C. Struppa, Alain Yger
Mathematics, Physics, and Computer Science Faculty Articles and Research
The notion of supershift (in itself a generalization of the notion of superoscillation arising in quantum mechanics) expresses the fact that the sampling of a function in an interval allows to compute the values of the function far from the interval. In this paper, we study the relation between supershift and real analyticity. We use a classical result due to Serge Bernstein to show that real analyticity for a complex-valued function implies a strong form of supershift. On the other hand, we use a parametric version of a result by Leonid Kantorovitch to show that the converse is not true. …
How Do We Observe Relational Observables?, Emily Adlam
How Do We Observe Relational Observables?, Emily Adlam
Mathematics, Physics, and Computer Science Faculty Articles and Research
In theories with a diffeomorphism symmetry, such as general relativity and canonical quantum gravity, it is often proposed that the empirical content is encoded in relational observables. But how do relational observables actually make contact with experience? I argue that this question can only be answered by providing a schematization of the observer which is appropriate for the context of a diffeomorphism-invariant theory. I suggest that this may require us to move away from a ‘passive awareness’ conception of consciousness towards a more agential conception, because there is a clear sense in which an embodied agent must experience herself as …
Artificially Intelligent Maxwell's Demon For Optimal Control Of Open Quantum Systems, Paolo A. Erdman, Robert Czupryniak, Bibek Bhandari, Andrew N. Jordan, Frank Noé, Jens Eisert, Giacomo Guarnieri
Artificially Intelligent Maxwell's Demon For Optimal Control Of Open Quantum Systems, Paolo A. Erdman, Robert Czupryniak, Bibek Bhandari, Andrew N. Jordan, Frank Noé, Jens Eisert, Giacomo Guarnieri
Mathematics, Physics, and Computer Science Faculty Articles and Research
Feedback control of open quantum systems is of fundamental importance for practical applications in various contexts, ranging from quantum computation to quantum error correction and quantum metrology. Its use in the context of thermodynamics further enables the study of the interplay between information and energy. However, deriving optimal feedback control strategies is highly challenging, as it involves the optimal control of open quantum systems, the stochastic nature of quantum measurement, and the inclusion of policies that maximize a long-term time- and trajectory-averaged goal. In this work, we employ a reinforcement learning approach to automate and capture the role of a …
Measurement Time Of Weak Measurements On Large Entangled Systems, Truong-Son P. Văn, Andrew N. Jordan, David W. Snoke
Measurement Time Of Weak Measurements On Large Entangled Systems, Truong-Son P. Văn, Andrew N. Jordan, David W. Snoke
Mathematics, Physics, and Computer Science Faculty Articles and Research
It is well established that starting only with strong, projective quantum measurements, experiments can be designed to allow weak measurements, which lead to a random walk between the possible final measurement outcomes. However, one can ask the reverse question: starting with only weak measurements, can all the results of standard strong measurements be recovered? Prior work has shown that some results can be, such as the Born rule for the probability of measurement outcomes as a function of wave intensity. In this paper, we show that another crucial result can be reproduced by purely weak measurements, namely, the collapse of …
A New Form Of Soft Supersymmetry Breaking?, Scott Chapman
A New Form Of Soft Supersymmetry Breaking?, Scott Chapman
Mathematics, Physics, and Computer Science Faculty Articles and Research
Starting with a supersymmetric U(N) × U(N) gauge theory built in N = 1 superspace, a nonsupersymmetric theory is obtained by “twisting” the gauginos into a different representation of the group than the gauge bosons. Despite the fact that this twisting breaks supersymmetry, it is still possible to construct an action that is holomorphic and invariant to local “twisted” gauge transformations in superspace. It is conjectured that these two properties may allow the theory to be free of quadratic divergences to all orders, despite a lack of supersymmetry. An explicit calculation shows that the theory is free of quadratic divergences …
Exploring The Accuracy Of Interferometric Quantum Measurements Under Conservation Laws, Nicolò Piccione, Maria Maffei, Andrew N. Jordan, Kater W. Murch, Alexia Auffèves
Exploring The Accuracy Of Interferometric Quantum Measurements Under Conservation Laws, Nicolò Piccione, Maria Maffei, Andrew N. Jordan, Kater W. Murch, Alexia Auffèves
Mathematics, Physics, and Computer Science Faculty Articles and Research
A (target) quantum system is often measured through observations performed on a second (meter) system to which the target is coupled. In the presence of global conservation laws holding on the joint meter-target system, the Wigner-Araki-Yanase theorem and its generalizations predict a lower bound on the measurement’s error (Ozawa’s bound). While practically negligible for macroscopic meters, it becomes relevant for microscopic ones. Here, we propose a simple interferometric setup, arguably within reach of present technology, in which a flying particle (a microscopic quantum meter) is used to measure a qubit by interacting with it in one arm of the interferometer. …
Separating A Particle's Mass From Its Momentum, Mordecai Waegell, Jeff Tollaksen, Yakir Aharonov
Separating A Particle's Mass From Its Momentum, Mordecai Waegell, Jeff Tollaksen, Yakir Aharonov
Mathematics, Physics, and Computer Science Faculty Articles and Research
The Quantum Cheshire Cat experiment showed that when weak measurements are performed on pre- and post-selected system, the counterintuitive result has been obtained that a neutron is measured to be in one place without its spin, and its spin is measured to be in another place without the neutron. A generalization of this effect is presented with a massive particle whose mass is measured to be in one place with no momentum, while the momentum is measured to be in another place without the mass. The new result applies to any massive particle, independent of its spin or charge. A …
High-Coherence Kerr-Cat Qubit In 2d Architecture, Ahmed Hajr, Bingcheng Qing, Ke Wang, Gerwin Koolstra, Zahra Pedramrazi, Ziqi Kang, Larry Chen, Long B. Nguyen, Christian Jünger, Noah Goss, Irwin Huang, Bibek Bhandari, Nicholas E. Frattini, Shruti Puri, Justin Dressel, Andrew N. Jordan, David I. Santiago, Irfan Siddiqi
High-Coherence Kerr-Cat Qubit In 2d Architecture, Ahmed Hajr, Bingcheng Qing, Ke Wang, Gerwin Koolstra, Zahra Pedramrazi, Ziqi Kang, Larry Chen, Long B. Nguyen, Christian Jünger, Noah Goss, Irwin Huang, Bibek Bhandari, Nicholas E. Frattini, Shruti Puri, Justin Dressel, Andrew N. Jordan, David I. Santiago, Irfan Siddiqi
Mathematics, Physics, and Computer Science Faculty Articles and Research
The Kerr-cat qubit is a bosonic qubit in which multiphoton Schrödinger cat states are stabilized by applying a two-photon drive to an oscillator with a Kerr nonlinearity. The suppressed bit-flip rate with increasing cat size makes this qubit a promising candidate to implement quantum error correction codes tailored for noise-biased qubits. However, achieving strong light-matter interactions necessary for stabilizing and controlling this qubit has traditionally required strong microwave drives that heat the qubit and degrade its performance. In contrast, increasing the coupling to the drive port removes the need for strong drives at the expense of large Purcell decay. By …
Optimal Radar Ranging Pulse To Resolve Two Reflectors, Andrew N. Jordan, John C. Howell, Achim Kempf, Shunxing Zhang, Derek White
Optimal Radar Ranging Pulse To Resolve Two Reflectors, Andrew N. Jordan, John C. Howell, Achim Kempf, Shunxing Zhang, Derek White
Mathematics, Physics, and Computer Science Faculty Articles and Research
Previous work established fundamental bounds on subwavelength resolution for the radar range resolution problem, called superradar [Phys. Rev. Appl. 20, 064046 (2023)]. In this work, we identify the optimal waveforms for distinguishing the range resolution between two reflectors of identical strength, leveraging results in quantum metrology. We discuss both the unnormalized optimal waveform as well as the best square-integrable pulse and their variants. Using orthogonal function theory, we give an explicit algorithm to optimize the wave pulse in finite time to have the best performance. We also explore range resolution estimation with unnormalized waveforms with multiparameter methods to …
Quantum Field Theory And The Limits Of Reductionism, Emily Adlam
Quantum Field Theory And The Limits Of Reductionism, Emily Adlam
Mathematics, Physics, and Computer Science Faculty Articles and Research
I suggest that the current situation in quantum field theory (QFT) provides some reason to question the universal validity of ontological reductionism. I argue that the renormalization group flow is reversible except at fixed points, which makes the relation between large and small distance scales quite symmetric in QFT, opening up at least the technical possibility of a non-reductionist approach to QFT. I suggest that some conceptual problems encountered within QFT may potentially be mitigated by moving to an alternative picture in which it is no longer the case that the large supervenes on the small. Finally, I explore some …
Madelung Mechanics And Superoscillations, Mordecai Waegell
Madelung Mechanics And Superoscillations, Mordecai Waegell
Mathematics, Physics, and Computer Science Faculty Articles and Research
In single-particle Madelung mechanics, the single-particle quantum state Ψ(⃗x, t) = R(⃗x, t)eiS(⃗x,t)/h is interpreted as comprising an entire conserved fluid of classical point particles, with local density R(⃗x, t)2 and local momentum ⃗∇S(⃗x, t) (where R and S are real). The Schrödinger equation gives rise to the continuity equation for the fluid, and the Hamilton–Jacobi equation for particles of the fluid, which includes an additional density-dependent quantum potential energy term Q(⃗x, t) = − ¯h2 2m ⃗∇R(⃗x,t) R(⃗x,t) , which is all that makes the fluid behavior nonclassical. In particular, the quantum potential can become negative and create a …
Superphenomena For Arbitrary Quantum Observables, Andrew N. Jordan, Yakir Aharonov, Daniele C. Struppa, Fabrizio Colombo, Irene Sabadini, Tomer Shushi, Jeff Tollaksen, John C. Howell, A. Nick Vamivakas
Superphenomena For Arbitrary Quantum Observables, Andrew N. Jordan, Yakir Aharonov, Daniele C. Struppa, Fabrizio Colombo, Irene Sabadini, Tomer Shushi, Jeff Tollaksen, John C. Howell, A. Nick Vamivakas
Mathematics, Physics, and Computer Science Faculty Articles and Research
Superoscillations occur when a globally band-limited function locally oscillates faster than its highest Fourier component. We generalize this effect to arbitrary quantum-mechanical operators as a weak value, where the preselected state is a superposition of eigenstates of the operator with eigenvalues bounded to a range, and the postselection state is a local position. Superbehavior of this operator occurs whenever the operator's weak value exceeds its eigenvalue bound. We give illustrative examples of this effect for total angular momentum and energy. In the latter case, we demonstrate a sequence of harmonic oscillator potentials where a finite-energy state converges everywhere on the …
Generation Of Kochen-Specker Contextual Sets In Higher Dimensions By Dimensional Upscaling Whose Complexity Does Not Scale With Dimension And Their Applications, Mladen Pavičić, Mordecai Waegell
Generation Of Kochen-Specker Contextual Sets In Higher Dimensions By Dimensional Upscaling Whose Complexity Does Not Scale With Dimension And Their Applications, Mladen Pavičić, Mordecai Waegell
Mathematics, Physics, and Computer Science Faculty Articles and Research
Recently, handling of contextual sets, in particular Kochen-Specker (KS) sets, in higher dimensions has been given an increasing attention, both theoretically and experimentally. However, methods of their generation are diverse, not generally applicable in every dimension, and of exponential complexity. Therefore, we design a dimensional upscaling method, whose complexity does not scale with dimension. As a proof of principle we generate manageable-sized KS master sets in up to 27 dimensional spaces and show that well over 32 dimensions can be reached. From these master sets we obtain an ample number of smaller KS sets. We discuss three kinds of applications …
Fundamental Mechanisms Of Energy Exchanges In Autonomous Measurements Based On Dispersive Qubit-Light Interaction, Nicolò Piccione, Maria Maffei, Xiayu Linpeng, Andrew N. Jordan, Kater W. Murch, Alexia Auffèves
Fundamental Mechanisms Of Energy Exchanges In Autonomous Measurements Based On Dispersive Qubit-Light Interaction, Nicolò Piccione, Maria Maffei, Xiayu Linpeng, Andrew N. Jordan, Kater W. Murch, Alexia Auffèves
Mathematics, Physics, and Computer Science Faculty Articles and Research
Measuring an observable which does not commute with the Hamiltonian of a quantum system usually modifies the mean energy of this system. In an autonomous measurement scheme, coupling the system to a quantum meter, the system's energy change must be compensated by the meter's energy change. Here, we theoretically study such an autonomous meter-system dynamics: a qubit interacting dispersively with a light pulse propagating in a one-dimensional waveguide. The phase of the light pulse is shifted, conditioned to the qubit's state along the 𝑧 direction, while the orientation of the qubit Hamiltonian is arbitrary. As the interaction is dispersive, photon …
A Realist Interpretation Of Unitarity In Quantum Gravity, Indrajit Sen, Stephon Alexander, Justin Dressel
A Realist Interpretation Of Unitarity In Quantum Gravity, Indrajit Sen, Stephon Alexander, Justin Dressel
Mathematics, Physics, and Computer Science Faculty Articles and Research
Unitarity is a difficult concept to implement in canonical quantum gravity because of state non-normalisability and the problem of time. We take a realist approach based on pilot-wave theory to address this issue in the Ashtekar formulation of the Wheeler–DeWitt equation. We use the postulate of a definite configuration in the theory to define a global time for the gravitational-fermionic system recently discussed in Alexander et al (2022 Phys. Rev. D 106 106012), by parameterising a variation of a Weyl-spinor that depends on the Kodama state. The total Hamiltonian constraint yields a time-dependent Schrodinger equation, without semi-classical approximations, which we …