Witnessing Objectivity on a Quantum Computer

Chisholm, Dario A.; García-Pérez, Guillermo; Rossi, Matteo A. C.; Maniscalco, Sabrina; Palma, G. Massimo

doi:10.48550/arxiv.2110.06243

Cited by 3 publications

(3 citation statements)

References 33 publications

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“…Results are consistent with this expectation. Similar strategy (and similarly positive results) was obtained in an emulation of quantum Darwinism on an IBM 5-qubit quantum computer (Chisholm et al, 2021) [ 186 ].…”

Section: Quantum Darwinismsupporting

confidence: 66%

Quantum Theory of the Classical: Einselection, Envariance, Quantum Darwinism and Extantons

Zurek

2022

Entropy

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Core quantum postulates including the superposition principle and the unitarity of evolutions are natural and strikingly simple. I show that—when supplemented with a limited version of predictability (captured in the textbook accounts by the repeatability postulate)—these core postulates can account for all the symptoms of classicality. In particular, both objective classical reality and elusive information about reality arise, via quantum Darwinism, from the quantum substrate. This approach shares with the Relative State Interpretation of Everett the view that collapse of the wavepacket reflects perception of the state of the rest of the Universe relative to the state of observer’s records. However, our “let quantum be quantum” approach poses questions absent in Bohr’s Copenhagen Interpretation that relied on the preexisting classical domain. Thus, one is now forced to seek preferred, predictable, hence effectively classical but ultimately quantum states that allow observers keep reliable records. Without such (i) preferred basis relative states are simply “too relative”, and the ensuing basis ambiguity makes it difficult to identify events (e.g., measurement outcomes). Moreover, universal validity of quantum theory raises the issue of (ii) the origin of Born’s rule, pk=|ψk|2, relating probabilities and amplitudes (that is simply postulated in textbooks). Last not least, even preferred pointer states (defined by einselection—environment—induced superselection)—are still quantum. Therefore, unlike classical states that exist objectively, quantum states of an individual system cannot be found out by an initially ignorant observer through direct measurement without being disrupted. So, to complete the `quantum theory of the classical’ one must identify (iii) quantum origin of objective existence and explain how the information about objectively existing states can appear to be essentially inconsequential for them (as it does for states in Newtonian physics) and yet matter in other settings (e.g., thermodynamics). I show how the mathematical structure of quantum theory supplemented by the only uncontroversial measurement postulate (that demands immediate repeatability—hence, predictability) leads to preferred states. These (i) pointer states correspond to measurement outcomes. Their stability is a prerequisite for objective existence of effectively classical states and for events such as quantum jumps. Events at hand, one can now enquire about their probability—the probability of a pointer state (or of a measurement record). I show that the symmetry of entangled states—(ii) entanglement—assisted invariance or envariance—implies Born’s rule. Envariance also accounts for the loss of phase coherence between pointer states. Thus, decoherence can be traced to symmetries of entanglement and understood without its usual tool—reduced density matrices. A simple and manifestly noncircular derivation of pk=|ψk|2 follows. Monitoring of the system by its environment in course of decoherence typically leaves behind multiple copies of its pointer states in the environment. Only pointer states can survive decoherence and can spawn such plentiful information-theoretic progeny. This (iii) quantum Darwinism allows observers to use environment as a witness—to find out pointer states indirectly, leaving systems of interest untouched. Quantum Darwinism shows how epistemic and ontic (coexisting in epiontic quantum state) separate into robust objective existence of pointer states and detached information about them, giving rise to extantons—composite objects with system of interest in the core and multiple records of its pointer states in the halo comprising of environment subsystems (e.g., photons) which disseminates that information throughout the Universe.

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Section: Quantum Darwinismsupporting

confidence: 66%

Quantum Theory of the Classical: Einselection, Envariance, Quantum Darwinism and Extantons

Zurek

2022

Entropy

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“…The SBS was identified in the many models of open quantum systems (see [16] and ref. therein) and its simulations on a quantum computer were demonstrated [17]. It was also shown that the objectivity is subjective across quantum reference frames [18] including its dynamical aspects [19].…”

Section: Introductionmentioning

confidence: 93%

Non-perfect propagation of information to noisy environment with self-evolution

Mironowicz,

Horodecki,

Horodecki

2022

Preprint

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“…The objective states with spectrum broadcast structure can be used as ideal "frames of reference" to which any real states can be compared. The SBS was identified in the many models of open quantum systems (see [17] and the references therein), and its simulations on a quantum computer were demonstrated [18]. It was also shown that the objectivity is subjective across quantum reference frames [19], including its dynamical aspects [20].…”

Section: Introductionmentioning

confidence: 93%

Non-Perfect Propagation of Information to a Noisy Environment with Self-Evolution

Mironowicz

Horodecki

2022

Entropy

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We study the non-perfect propagation of information for evolving a low-dimensional environment that includes self-evolution as well as noisy initial states and analyse the interrelations between the degree of objectivization and environment parameters. In particular, we consider an analytical model of three interacting qubits and derive its objectivity parameters. The numerical analysis shows that the quality of the spectrum broadcast structure formed during the interaction may exhibit non-monotonicity both in the speed of self-dynamics of the environment as well as its mixedness. The former effect is particularly strong, showing that—considering part of the environment as a measurement apparatus—an increase of the external magnetic field acting on the environment may turn the vague measurement into close to ideal. The above effects suggest that quantum objectivity may appear after increasing the dynamics of the environment, although not with respect to the pointer basis, but some other, which we call the generalized pointer or indicator basis. Furthermore, it seems also that, when the objectivity is poor, it may be improved, at least by some amount, by increasing the thermal noise. We provide further evidence of this by analysing the upper bounds on distance to the set of states representing perfect objectivity in the case of a higher number of qubits.

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Witnessing Objectivity on a Quantum Computer

Cited by 3 publications

References 33 publications

Quantum Theory of the Classical: Einselection, Envariance, Quantum Darwinism and Extantons

Quantum Theory of the Classical: Einselection, Envariance, Quantum Darwinism and Extantons

Non-perfect propagation of information to noisy environment with self-evolution

Non-Perfect Propagation of Information to a Noisy Environment with Self-Evolution

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