Unobservable causal loops as a way to explain both the quantum computational speedup and quantum nonlocality

• URL: http://arxiv.org/abs/2011.14680v10
• Date: Mon, 17 May 2021 17:37:33 GMT
• Title: Unobservable causal loops as a way to explain both the quantum computational speedup and quantum nonlocality
• Authors: Giuseppe Castagnoli
• Abstract summary: We consider the reversible processes between two one-to-one correlated measurement outcomes. We argue that the quantum description of these processes mathematically describes the correlation but leaves the causal structure that physically ensures it free. Time-symmetrization leaves the ordinary quantum description but shows that it is the quantum superposition of unobservable time-symmetrization instances.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We consider the reversible processes between two one-to-one correlated measurement outcomes which underly both problem-solving and quantum nonlocality. In the former case the two outcomes are the setting and the solution of the problem, in the latter those of measuring a pair of maximally entangled observables whose subsystems are space separate. We argue that the quantum description of these processes mathematically describes the correlation but leaves the causal structure that physically ensures it free, also of violating the time-symmetry required of the description of a reversible process. It would therefore be incomplete and could be completed by time-symmetrizing it. This is done by assuming that the two measurements evenly contribute to selecting the pair of correlated measurement outcomes. Time-symmetrization leaves the ordinary quantum description unaltered but shows that it is the quantum superposition of unobservable time-symmetrization instances whose causal structure is completely defined. Each instance is a causal loop: causation goes from the initial to the final measurement outcome and then back from the final to the initial outcome. In the speedup, all is as if the problem solver knew in advance half of the information about the solution she will produce in the future and could use this knowledge to produce the solution with fewer computation steps. In nonlocality, the measurement on either subsystem retrocausally and locally changes the state of both subsystems when the two were not yet spatially separate. This locally causes the correlation between the two future measurement outcomes.

Related papers

• Measuring the Evolution of Entanglement in Compton Scattering [101.11630543545151]
  The behavior of quantum entanglement during scattering is identical to the behavior of initially classically correlated photons up to a constant factor equal to two. Our dedicated experiment with photons confirms these results and explains the "Puzzle of Decoherence" observed recently.
  arXiv  Detail & Related papers  (2024-06-20T14:21:23Z)
• Quantifying measurement-induced quantum-to-classical crossover using an open-system entanglement measure [49.1574468325115]
  We study the entanglement of a single particle under continuous measurements. We find that the entanglement at intermediate time scales shows the same qualitative behavior as a function of the measurement strength.
  arXiv  Detail & Related papers  (2023-04-06T09:45:11Z)
• Quantum Causal Inference with Extremely Light Touch [0.0]
  We give an explicit quantum causal inference scheme using quantum observations alone. We derive a closed-form expression for the space-time pseudo-density matrix associated with many times and qubits. We prove that if there is no signalling between two subsystems, the associated reduced state of the pseudo-density matrix cannot have negativity.
  arXiv  Detail & Related papers  (2023-03-19T02:59:05Z)
• Evolution of many-body systems under ancilla quantum measurements [58.720142291102135]
  We study the concept of implementing quantum measurements by coupling a many-body lattice system to an ancillary degree of freedom. We find evidence of a disentangling-entangling measurement-induced transition as was previously observed in more abstract models.
  arXiv  Detail & Related papers  (2023-03-13T13:06:40Z)
• Bell inequalities with overlapping measurements [52.81011822909395]
  We study Bell inequalities where measurements of different parties can have overlap. This allows to accommodate problems in quantum information. The scenarios considered show an interesting behaviour with respect to Hilbert space dimension, overlap, and symmetry.
  arXiv  Detail & Related papers  (2023-03-03T18:11:05Z)
• Measurement-induced phase transitions on dynamical quantum trees [0.0]
  We show a transition at a nontrivial value of the measurement strength, with the real measurement case exhibiting a smaller entangling phase. An intriguing difference between the two cases is that the real measurement case lies at the boundary between two distinct types of critical scaling. We propose a protocol for realizing a measurement phase transition experimentally via an expansion process.
  arXiv  Detail & Related papers  (2022-10-13T18:00:54Z)
• Finite resolution ancilla-assisted measurements of quantum work distributions [77.34726150561087]
  We consider an ancilla-assisted protocol measuring the work done on a quantum system driven by a time-dependent Hamiltonian. We consider system Hamiltonians which both commute and do not commute at different times, finding corrections to fluctuation relations like the Jarzynski equality and the Crooks relation.
  arXiv  Detail & Related papers  (2021-11-30T15:08:25Z)
• The quantum mechanical notion of unobservable causal loop and the anthropic principle [0.0]
  It can be argued that the ordinary description of the reversible quantum process between two one-to-one correlated measurement outcomes is incomplete. We show that it is the quantum superposition of unobservable time-symmetrized instances whose causal structure is completely defined.
  arXiv  Detail & Related papers  (2021-03-04T17:30:54Z)
• Stochastic process emerged from lattice fermion systems by repeated measurements and large-time limit [0.0]
  In quantum theory, measurements may suppress Hamiltonian dynamics of a system. In the present paper, we consider the long time repeated measurements and the dynamics of quantum body systems.
  arXiv  Detail & Related papers  (2020-07-28T01:46:36Z)
• The role of boundary conditions in quantum computations of scattering observables [58.720142291102135]
  Quantum computing may offer the opportunity to simulate strongly-interacting field theories, such as quantum chromodynamics, with physical time evolution. As with present-day calculations, quantum computation strategies still require the restriction to a finite system size. We quantify the volume effects for various $1+1$D Minkowski-signature quantities and show that these can be a significant source of systematic uncertainty.
  arXiv  Detail & Related papers  (2020-07-01T17:43:11Z)
• Non-destructively probing the thermodynamics of quantum systems with qumodes [0.6144680854063939]
  In quantum systems there is often a destruction of the system itself due to the means of measurement. One approach to circumventing this is the use of ancillary probes that couple to the system under investigation. We highlight means by which continuous variable quantum modes (qumodes) can be employed to probe the thermodynamics of quantum systems in and out of equilibrium.
  arXiv  Detail & Related papers  (2017-07-13T17:57:11Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.