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Full-Text Articles in Physics
Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel
Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel
Mathematics, Physics, and Computer Science Faculty Articles and Research
Out-of-time-ordered correlators (OTOCs) have been proposed as a tool to witness quantum information scrambling in many-body system dynamics. These correlators can be understood as averages over nonclassical multitime quasiprobability distributions (QPDs). These QPDs have more information and their nonclassical features witness quantum information scrambling in a more nuanced way. However, their high dimensionality and nonclassicality make QPDs challenging to measure experimentally. We focus on the topical case of a many-qubit system and show how to obtain such a QPD in the laboratory using circuits with three and four sequential measurements. Averaging distinct values over the same measured distribution reveals either …
Benchmarks Of Nonclassicality For Qubit Arrays, Mordecai Waegell, Justin Dressel
Benchmarks Of Nonclassicality For Qubit Arrays, Mordecai Waegell, Justin Dressel
Mathematics, Physics, and Computer Science Faculty Articles and Research
We present a set of practical benchmarks for N-qubit arrays that economically test the fidelity of achieving multi-qubit nonclassicality. The benchmarks are measurable correlators similar to two-qubit Bell correlators, and are derived from a particular set of geometric structures from the N-qubit Pauli group. These structures prove the Greenberger–Horne–Zeilinger (GHZ) theorem, while the derived correlators witness genuine N-partite entanglement and establish a tight lower bound on the fidelity of particular stabilizer state preparations. The correlators need only M ≤ N + 1 distinct measurement settings, as opposed to the 22N − 1 settings that would normally be …
A Panorama On Superoscillations, Fabrizio Colombo, Irene Sabadini, Daniele Carlo Struppa
A Panorama On Superoscillations, Fabrizio Colombo, Irene Sabadini, Daniele Carlo Struppa
Mathematics, Physics, and Computer Science Faculty Articles and Research
Purpose of this note is to give an overview on superoscillating sequences and some of their properties. We discuss their persistence in time under Schrödinger equation, we propose various classes of superoscillating functions and we also briefly mention how they can be used to approximate some generalized functions.
Out-Of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling, José Raúl González Alonso, Nicole Yunger Halpern, Justin Dressel
Out-Of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling, José Raúl González Alonso, Nicole Yunger Halpern, Justin Dressel
Mathematics, Physics, and Computer Science Faculty Articles and Research
Out-of-time-ordered correlators (OTOCs) have received considerable recent attention as qualitative witnesses of information scrambling in many-body quantum systems. Theoretical discussions of OTOCs typically focus on closed systems, raising the question of their suitability as scrambling witnesses in realistic open systems. We demonstrate empirically that the nonclassical negativity of the quasiprobability distribution (QPD) behind the OTOC is a more sensitive witness for scrambling than the OTOC itself. Nonclassical features of the QPD evolve with timescales that are robust with respect to decoherence and are immune to false positives caused by decoherence. To reach this conclusion, we numerically simulate spinchain dynamics and …
Why Physical Understanding Should Precede The Mathematical Formalism—Conditional Quantum Probabilities As A Case-Study, Yakir Aharonov, Eliahu Cohen, David H. Oaknin
Why Physical Understanding Should Precede The Mathematical Formalism—Conditional Quantum Probabilities As A Case-Study, Yakir Aharonov, Eliahu Cohen, David H. Oaknin
Mathematics, Physics, and Computer Science Faculty Articles and Research
Conditional probabilities in quantum systems which have both initial and final boundary conditions are commonly evaluated using the Aharonov–Bergmann–Lebowitz rule. In this short note, we present a seemingly disturbing paradox that appears when applying the rule to systems with slightly broken degeneracies. In these cases, we encounter a singular limit—the probability “jumps” when going from perfect degeneracy to negligibly broken one. We trace the origin of the paradox and solve it from both traditional and modern perspectives in order to highlight the physics behind it: the necessity to take into account the finite resolution of the measuring device. As a …