Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session U09: Quantum Foundations IIIFocus

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Sponsoring Units: DQI Chair: Flaminia Giacomini, Perimeter Inst for Theo Phys Room: 106 
Thursday, March 5, 2020 2:30PM  2:42PM 
U09.00001: Time in Quantum Information Mohammad Ansari, Alwin van Steensel, Yuli Nazarov Currently 'time' does not play any essential role in quantum information theory. In this sense, the theory is underdeveloped, similarly to how quantum physics was before Erwin Schrodinger introduced his famous evolution of wave functions. I will desribe the problem of defining timeevolution in quantum information theory, specially for a central measures in the theory, i.e. Renyi entropy. I use a newlydeveloped replica trick formalism, namely 'Multiparallel World (MW)' formalism, that revolutionizes the theory. This formalism is one of the first attempts to introduce 'time evolution' for information transfer. With the total entropy being conserved in a closed system, entropy can flow internally between subsystems and I show that this flow is not limited to physical correlations as literature suggests, in fact information correlations are also involved. The mere existence of this new class of correlations allows for faster and slower information tranfer. 
Thursday, March 5, 2020 2:42PM  2:54PM 
U09.00002: Violations of macroscopic local reality, time and the Qfunction Margaret Reid, Manushan Thenabadu, Peter Drummond A macroscopic superposition state would appear to be inconsistent with the classical concept of macroscopic realism. Leggett and Garg proposed tests of macroscopic realism based on the validity of a second premise: (macroscopic) noninvasive measureability. Here, we consider tests of macroscopic realism where the second premise is replaced by that of macroscopic locality. Extending results obtained for NOON states [1], we show how one can falsify macroscopic local realism, by using Bell inequalities for catstates where the choice of polarizer setting is replaced with a choice of timeofevolution through a nonlinear medium. Different to the original Bell tests, here the outcomes of all relevant measurements are distinct by N bosons at each site, or else are wellseparated in phase space. This motivates us to consider a model of reality based on the Q function. In that model, measurement is described by a dynamical interaction where sharp eigenvalues emerge for sufficient amplification, and Bell violations arise, there being backwardsintime effects arising through negative diffusion terms [2]. 
Thursday, March 5, 2020 2:54PM  3:30PM 
U09.00003: Asymmetry in cause and effect in a quantum world Invited Speaker: Jayne Thompson How can we observe an asymmetry in the temporal order of events when physics at the quantum level is timesymmetric? The source of time's barbed arrow is a longstanding puzzle. Causal asymmetry offers a provocative perspective. It asks how Occam's razor can privilege one temporal direction over another. That is, if we want to make statisticall correct future predictions then what is the minimum past information we must store? Are we forced to store more data if we model events in one particular temporal order over the other? 
Thursday, March 5, 2020 3:30PM  3:42PM 
U09.00004: Time operators and time crystals: selfadjointness by topology change Keiji Nakatsugawa, Toshiyuki Fujii, Avadh Saxena, Satoshi Tanda In the standard formulation of quantum mechanics and quantum field theory, time is not an observable but merely a parameter. There are two open problems which can promote time to an observable, namely 1) how to define selfadjoint time operators and 2) how to obtain systems called quantum time crystals. 
Thursday, March 5, 2020 3:42PM  3:54PM 
U09.00005: Classicallyforbidden probability flow in the quantum reentry problem Arseni Goussev The laws of quantum mechanics allow for a moving particle to temporarily reverse the direction of its motion even in the absence of any external force. A wellknown manifestation of this counterintuitive phenomenon is the socalled quantum backflow effect, whereby the probability of finding a particle "on the left" increases with time despite the particle velocity pointing "to the right". In my talk, I will provide another clearcut demonstration of nonconstancy of the direction of motion of a free particle. I will show that the freespace expansion of a quantum wave packet, initially confined to an interval, may be nonmonotonous: The probability density may sometimes flow back into (or reenter) the interval. The supremum of the classicallyforbidden probability flow in this reentry problem appears to be the same as in the case of quantum backflow. 
Thursday, March 5, 2020 3:54PM  4:06PM 
U09.00006: Indefinite Causal Orderings for Quantum Depolarizing Channel Identification Michael Frey Quantum channel identification (QCI) is the statistical estimation of channel parameters, accomplished by passing probe systems in prepared states through the quantum channel. Indefinite causal ordering (ICO) is a channel probing scheme in which copies of a quantum channel are physically or logically arranged so that the path through them is a superposition of different possible paths. Channel probing is known to be aided in a strong sense by ICO in the case of the qudit (ddimensional) depolarizing channel. Specifically, ICOassisted probing increases the quantum Fisher information (QFI) in the processed probe state about the unknown parameter(s), with increasing order indefiniteness yielding correspondingly greater QFI. Investigations up until now have involved just superpositions of forward and reverse channel orderings; for example, three channel copies, A, B, and C, in a superposition of orderings ABC and CBA. Alternatively, these channels copies can be cyclically indefinitely ordered: a superposition of ABC, BCA, and CAB. The present work compares the effectiveness (QFI) of disparate competing ICOs for probing the qudit depolarizing channel. The QFIs associated with these competing ICOs are expressed analytically. 
Thursday, March 5, 2020 4:06PM  4:18PM 
U09.00007: Contextuality in noninteracting measurement Sacha Greenfield, Mordecai Waegell, Justin Dressel Noninteracting measurement is a phenomenon of seemingly nonlocal information transfer that arises for a single photon in a cascade of twoarm interferometers. Since contextuality has been identified as a resource for quantum informational tasks, it is reasonable to posit that noninteracting measurement requires contextuality in some form. We confirm this suspicion for the case of imbalanced beam splitters and discuss the exception that admits a noncontextual model. In contrast to existing proofs of contextuality for a single qubit, this scenario involves only pure states and sharp measurements. 
Thursday, March 5, 2020 4:18PM  4:30PM 
U09.00008: A tight quantum speed limit for open quantum dynamics Yusef Maleki

Thursday, March 5, 2020 4:30PM  4:42PM 
U09.00009: The Heisenberg Interpretation of Quantum Mechanics Armin Nikkhah Shirazi In his book `Physics and Philosophy', Werner Heisenberg posited a distinction between the quantum and the classical worlds, which he characterized in terms of "potentialities or possibilities" versus "things and facts". However, the standard quantum formalism does not express such distinctions. 
Thursday, March 5, 2020 4:42PM  4:54PM 
U09.00010: Experimental Comparison of Bohmlike Theories with Different Ontologies Arthur Ou Teen Pang, Hugo Ferretti, Noah LupuGladstein, WengKian Tham, Aharon Brodutch, Kent AG BonsmaFisher, John Edward Sipe, Aephraim M Steinberg The de BroglieBohm theory is a hidden variable interpretation of quantum mechanics which involves particles moving through space with definite trajectories. This theory singles out position as the primary ontological variable. Mathematically, it is possible to construct a similar theory where particles are moving through momentum space, and momentum is singled out as the primary ontological variable. In this paper we experimentally show how the two theories lead to different ontological descriptions. We construct the putative particle trajectories for a twoslit experiment in both the position and momentum space theories by simulating particle dynamics with coherent light. Using a method for constructing trajectories through the primary and derived (i.e. nonprimary) spaces, we compare the ontological pictures offered by the two theories and show that they do not agree. This contradictory behaviour brings into question which ontology for Bohmian mechanics is to be preferred. 
Thursday, March 5, 2020 4:54PM  5:06PM 
U09.00011: Quantum Mechanical ResetObserver Reset, not Observation, results in QM WaveParticle Duality in MultiSlit experiments Martin Alpert A quantum mechanical mechanism based on statistical mechanics is proposed. It is based on corresponding and reciprocal changes in the number of states with associated energy changes at the observer and observed at reset and observation of the observer. The change in the number of states is different than the value of the observation. Each state is a possible input to the system. Bits, as a measure of information content, are considered the discrete cell size of a state. An experiment is proposed to determine where and when energy changes occur and how they are related to the observer and observed during the entire measurement process. A related experiment is proposed to determine timing between changes in the number of states. No time delay would indicate this is an entangled process and explain delayed choice observations. Bits not stored are lost, so when the number of inputs is greater than the number of outputs, an energy change occurs, and interference is observed (wave characteristics). If the number of inputs equals the number of outputs, no energy change occurs, and no interference is observed (particle characteristics). The theory, if verified, would further the understanding of the measurement process and entanglementâ€™s involvement in the process. 
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