Reassessing the advantage of indefinite causal orders for quantum metrology

• URL: http://arxiv.org/abs/2312.12172v3
• Date: Wed, 1 May 2024 08:20:15 GMT
• Title: Reassessing the advantage of indefinite causal orders for quantum metrology
• Authors: Raphaël Mothe, Cyril Branciard, Alastair A. Abbott,
• Abstract summary: In this work, we argue that some of these advantages in fact do not hold if a fairer comparison is made. We consider a framework that allows for a proper comparison between the performance of different classes of indefinite causal order processes.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: The quantum switch, the canonical example of a process with indefinite causal order, has been claimed to provide various advantages over processes with definite causal orders for some particular tasks in the field of quantum metrology. In this work, we argue that some of these advantages in fact do not hold if a fairer comparison is made. To this end, we consider a framework that allows for a proper comparison between the performance, quantified by the quantum Fisher information, of different classes of indefinite causal order processes and that of causal strategies on a given metrological task. More generally, by considering the recently proposed classes of circuits with classical or quantum control of the causal order, we come up with different examples where processes with indefinite causal order offer (or not) an advantage over processes with definite causal order, qualifying the interest of indefinite causal order regarding quantum metrology. As it turns out, for a range of examples, the class of quantum circuits with quantum control of causal order, which are known to be physically realizable, is shown to provide a strict advantage over causally ordered quantum circuits as well as over the class of quantum circuits with causal superposition. Thus, the consideration of this class provides new evidence that indefinite causal order strategies can strictly outperform definite causal order strategies in quantum metrology.

Related papers

• Quantum Query Complexity of Boolean Functions under Indefinite Causal Order [0.9208007322096533]
  We study the query complexity of Boolean functions under general higher order quantum computations. We show that the recently introduced class of quantum circuits with quantum control of causal order cannot lead to any reduction in query complexity. We find some functions for which the minimum error with which they can be computed using two queries is strictly lower when exploiting causally indefinite supermaps.
  arXiv  Detail & Related papers  (2023-07-18T13:12:55Z)
• Reassessing thermodynamic advantage from indefinite causal order [0.0]
  Indefinite causal order is a key feature involved in the study of quantum higher order transformations. We show that indefinite causal order is not necessary for the reported increase in free energy and ergotropy.
  arXiv  Detail & Related papers  (2022-08-05T14:41:49Z)
• Entanglement and coherence in Bernstein-Vazirani algorithm [58.720142291102135]
  Bernstein-Vazirani algorithm allows one to determine a bit string encoded into an oracle. We analyze in detail the quantum resources in the Bernstein-Vazirani algorithm. We show that in the absence of entanglement, the performance of the algorithm is directly related to the amount of quantum coherence in the initial state.
  arXiv  Detail & Related papers  (2022-05-26T20:32:36Z)
• No-signalling constrains quantum computation with indefinite causal structure [45.279573215172285]
  We develop a formalism for quantum computation with indefinite causal structures. We characterize the computational structure of higher order quantum maps. We prove that these rules, which have a computational and information-theoretic nature, are determined by the more physical notion of the signalling relations between the quantum systems.
  arXiv  Detail & Related papers  (2022-02-21T13:43:50Z)
• Interactive Protocols for Classically-Verifiable Quantum Advantage [46.093185827838035]
  "Interactions" between a prover and a verifier can bridge the gap between verifiability and implementation. We demonstrate the first implementation of an interactive quantum advantage protocol, using an ion trap quantum computer.
  arXiv  Detail & Related papers  (2021-12-09T19:00:00Z)
• Experimental violations of Leggett-Garg's inequalities on a quantum computer [77.34726150561087]
  We experimentally observe the violations of Leggett-Garg-Bell's inequalities on single and multi-qubit systems. Our analysis highlights the limits of nowadays quantum platforms, showing that the above-mentioned correlation functions deviate from theoretical prediction as the number of qubits and the depth of the circuit grow.
  arXiv  Detail & Related papers  (2021-09-06T14:35:15Z)
• Quantum circuits with classical versus quantum control of causal order [0.0]
  It is known that quantum supermaps which respect a definite, predefined causal order between their input operations correspond to fixed-order quantum circuits. Here we identify two new types of circuits that naturally generalise the fixed-order case. We show that quantum circuits with quantum control of causal order can only generate "causal" correlations, compatible with a well-defined causal order.
  arXiv  Detail & Related papers  (2021-01-21T19:00:06Z)
• Experiments on quantum causality [0.0]
  Quantum causality extends the conventional notion of fixed causal structure by allowing channels and operations to act in an indefinite causal order. In this review, we will walk through the basic theory of indefinite causal order and focus on experiments that rely on a physically realisable indefinite causal ordered process.
  arXiv  Detail & Related papers  (2020-09-01T15:25:26Z)
• A no-go theorem for superpositions of causal orders [0.0]
  Quantum control implies that a controlling system carries the which-order information. Can the order of two events be in a pure superposition, uncorrelated with any other system? A pure superposition of any pair of Markovian, unitary processes with equal local dimensions and different causal orders is not a valid process.
  arXiv  Detail & Related papers  (2020-08-14T06:29:05Z)
• Boundaries of quantum supremacy via random circuit sampling [69.16452769334367]
  Google's recent quantum supremacy experiment heralded a transition point where quantum computing performed a computational task, random circuit sampling. We examine the constraints of the observed quantum runtime advantage in a larger number of qubits and gates.
  arXiv  Detail & Related papers  (2020-05-05T20:11:53Z)
• Genuine quantum networks: superposed tasks and addressing [68.8204255655161]
  We show how to make quantum networks, both standard and entanglement-based, genuine quantum. We provide them with the possibility of handling superposed tasks and superposed addressing.
  arXiv  Detail & Related papers  (2020-04-30T18:00:06Z)

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.