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Full-Text Articles in Physics
What Is Nonlocal In Counterfactual Quantum Communication?, Yakir Aharonov, Daniel Rohrlich
What Is Nonlocal In Counterfactual Quantum Communication?, Yakir Aharonov, Daniel Rohrlich
Mathematics, Physics, and Computer Science Faculty Articles and Research
We revisit the “counterfactual quantum communication” of Salih et al. [1], who claim that an observer “Bob” can send one bit of information to a second observer “Alice” without any physical particle traveling between them. We show that a locally conserved, massless current—specifically, a current of modular angular momentum, Lz mod 2ℏ—carries the one bit of information. We integrate the flux of Lz mod 2ℏ from Bob to Alice and show that it equals one of the two eigenvalues of Lz mod 2ℏ, either 0 or ℏ, thus precisely accounting for the one bit of information he sends her.We previously …
Always-On Quantum Error Tracking With Continuous Parity Measurements, Razieh Mohseninia, Jing Yang, Irfan Siddiqi, Andrew N. Jordan, Justin Dressel
Always-On Quantum Error Tracking With Continuous Parity Measurements, Razieh Mohseninia, Jing Yang, Irfan Siddiqi, Andrew N. Jordan, Justin Dressel
Mathematics, Physics, and Computer Science Faculty Articles and Research
We investigate quantum error correction using continuous parity measurements to correct bit-flip errors with the three-qubit code. Continuous monitoring of errors brings the benefit of a continuous stream of information, which facilitates passive error tracking in real time. It reduces overhead from the standard gate-based approach that periodically entangles and measures additional ancilla qubits. However, the noisy analog signals from continuous parity measurements mandate more complicated signal processing to interpret syndromes accurately. We analyze the performance of several practical filtering methods for continuous error correction and demonstrate that they are viable alternatives to the standard ancilla-based approach. As an optimal …
The Operational Choi-Jamio Lkowski Isomorphism, Emily Adlam
The Operational Choi-Jamio Lkowski Isomorphism, Emily Adlam
Mathematics, Physics, and Computer Science Faculty Articles and Research
In this article, I use an operational formulation of the Choi–Jamiołkowski isomorphism to explore an approach to quantum mechanics in which the state is not the fundamental object. I first situate this project in the context of generalized probabilistic theories and argue that this framework may be understood as a means of drawing conclusions about the intratheoretic causal structure of quantum mechanics which are independent of any specific ontological picture. I then give an operational formulation of the Choi–Jamiołkowski isomorphism and show that, in an operational theory which exhibits this isomorphism, several features of the theory which are usually regarded …
A Twist On Broken U(3) × U(3) Supersymmetry, Scott Chapman
A Twist On Broken U(3) × U(3) Supersymmetry, Scott Chapman
Mathematics, Physics, and Computer Science Faculty Articles and Research
What symmetry breaking would be required for gauginos from a supersymmetric theory to behave like left-handed quarks of the Standard Model? Starting with a supersymmetric SU(3)xSU(3)xU(1)xU(1) gauge theory, the 18 adjoint-representation gauginos are replaced with 2 families of 9 gauginos in the (3,3*) representation of the group. After this explicit breaking of supersymmetry, two-loop quadratic divergences still cancel at a unification scale. Coupling constant unification is supported by deriving the theory from an SU(3)xSU(3)xSU(3)xSU(3) Grand Unified Theory (GUT). Sin2 of the Weinberg angle for the GUT is 1/4 rather than 3/8, leading to a lower unification scale than usually …
Noncontextuality Inequalities From Antidistinguishability, Matthew S. Leifer, Cristhiano Duarte
Noncontextuality Inequalities From Antidistinguishability, Matthew S. Leifer, Cristhiano Duarte
Mathematics, Physics, and Computer Science Faculty Articles and Research
Noncontextuality inequalities are usually derived from the distinguishability properties of quantum states, i.e., their orthogonality. Here, we show that antidistinguishability can also be used to derive noncontextuality inequalities. The Yu-Oh 13-ray noncontextuality inequality can be rederived and generalized as an instance of our antidistinguishability method. For some sets of states, the antidistinguishability method gives tighter bounds on noncontextual models than just considering orthogonality, and the Hadamard states provide an example of this. We also derive noncontextuality inequalities based on mutually unbiased bases and symmetric informationally complete positive operator-valued measures. Antidistinguishability based inequalities were initially discovered as overlap bounds for the …
Magnetic Forces In The Absence Of A Classical Magnetic Field, Ismael L. Paiva, Yakir Aharonov, Jeff Tollaksen, Mordecai Waegell
Magnetic Forces In The Absence Of A Classical Magnetic Field, Ismael L. Paiva, Yakir Aharonov, Jeff Tollaksen, Mordecai Waegell
Mathematics, Physics, and Computer Science Faculty Articles and Research
It is shown that, in some cases, the effect of discrete distributions of flux lines in quantum mechanics can be associated with the effect of continuous distributions of magnetic fields with special symmetries. In particular, flux lines with an arbitrary value of magnetic flux can be used to create energetic barriers, which can be used to confine quantum systems in specially designed configurations. This generalizes a previous work where such energy barriers arose from flux lines with half-integer fluxons. Furthermore, it is shown how the Landau levels can be obtained from a two-dimensional grid of flux lines. These results suggest …
Footprints Of Quantum Pigeons, Gregory Reznick, Shrobona Bagchi, Justin Dressel, Lev Vaidman
Footprints Of Quantum Pigeons, Gregory Reznick, Shrobona Bagchi, Justin Dressel, Lev Vaidman
Mathematics, Physics, and Computer Science Faculty Articles and Research
We show that in the mathematical framework of the quantum theory, the classical pigeonhole principle can be violated more directly than previously suggested, i.e., in a setting closer to the traditional statement of the principle. We describe how the counterfactual reasoning of the paradox may be operationally grounded in the analysis of the tiny footprints left in the environment by the pigeons. After identifying the drawbacks of recent experiments of the quantum pigeonhole effect, we argue that a definitive experimental violation of the pigeonhole principle is still needed and propose such an implementation using modern quantum computing hardware: a superconducting …
Reformulating Bell's Theorem: The Search For A Truly Local Quantum Theory, Mordecai Waegell, Kelvin J. Mcqueen
Reformulating Bell's Theorem: The Search For A Truly Local Quantum Theory, Mordecai Waegell, Kelvin J. Mcqueen
Philosophy Faculty Articles and Research
The apparent nonlocality of quantum theory has been a persistent concern. Einstein et al. (1935) and Bell (1964) emphasized the apparent nonlocality arising from entanglement correlations. While some interpretations embrace this nonlocality, modern variations of the Everett-inspired many worlds interpretation try to circumvent it. In this paper, we review Bell's “no-go” theorem and explain how it rests on three axioms, local causality, no superdeterminism, and one world. Although Bell is often taken to have shown that local causality is ruled out by the experimentally confirmed entanglement correlations, we make clear that it is the conjunction of the …