Quantum state smoothing when Alice assumes the wrong type of monitoring by Bob

• URL: http://arxiv.org/abs/2506.15951v1
• Date: Thu, 19 Jun 2025 01:33:14 GMT
• Title: Quantum state smoothing when Alice assumes the wrong type of monitoring by Bob
• Authors: Areeya Chantasri, Kiarn T. Laverick, Howard M. Wiseman,
• Abstract summary: We show that the accuracy of Alice's estimate of the true state depends strongly on her setup, Bob's actual setup, and the wrongly assumed setup.<n>We show numerically that in some cases the wrong smoothing is almost as accurate as the right smoothing, but in other cases much less accurate, even being less accurate than Alice's filtered estimate.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: An open quantum system leaks information into its environment. In some circumstances it is possible for an observer, say Alice, to recover that information, as a classical measurement record, in a variety of different ways, using different experimental setups. The optimal way for Alice to estimate the quantum state at time $t$ from the record before $t$ is known as quantum filtering. Recently, a version of quantum smoothing, in which Alice estimates the state at time $t$ using her record on both sides of $t$, has been developed. It requires Alice to make optimal inferences about the pre-$t$ record of a second observer, say Bob, who recovers whatever information Alice does not. But for Alice to make this inference, she needs to know Bob's setup. In this paper we consider what happens if Alice is mistaken in her assumption about Bob's setup. We show that the accuracy -- as measured by the Trace-Squared-Deviation, of Alice's estimate of the true state (i.e., the state conditioned on her and Bob's pre-$t$ records) -- depends strongly on her setup, Bob's actual setup, and the wrongly assumed setup. Using resonance fluorescence as a model system, we show numerically that in some cases the wrong smoothing is almost as accurate as the right smoothing, but in other cases much less accurate, even being less accurate than Alice's filtered estimate. Curiously, in some of the latter cases the fidelity of Alice's wrong estimate with the true state is actually higher than that of her right estimate. We explain this, and other features we observe numerically, by some simple analytical arguments.

Related papers

• Photonic implementation of the quantum Morra game [69.65384453064829]
  We study a faithful translation of a two-player quantum Morra game, which builds on previous work by including the classical game as a special case. We propose a natural deformation of the game in the quantum regime in which Alice has a winning advantage, breaking the balance of the classical game. We discuss potential applications of the quantum Morra game to the study of quantum information and communication.
  arXiv  Detail & Related papers  (2023-11-14T19:41:50Z)
• Quantum advantage in a unified scenario and secure detection of resources [49.1574468325115]
  We consider a single communication task to study different approaches of observing quantum advantage.<n>In our task, there are three parties - the Manager, Alice, and Bob.<n>We show that the goal of the task can be achieved when Alice sends a qubit.
  arXiv  Detail & Related papers  (2023-09-22T23:06:20Z)
• On Quantum Steering and Wigner Negativity [0.0]
  We investigate how both are intertwined in the context of the conditional generation of Wigner negativity. We show that quantum correlations are in general not necessary for the conditional generation of Wigner negativity.
  arXiv  Detail & Related papers  (2022-11-25T13:35:33Z)
• Identifying the value of a random variable unambiguously: Quantum versus classical approaches [44.99833362998488]
  Quantum resources may provide advantage over their classical counterparts. We construct such a task based on a game, mediated by Referee and played between Alice and Bob. We show that if Alice sends limited amount of classical information then the game cannot be won while the quantum analogue of the limited amount of classical information' is sufficient for winning the game.
  arXiv  Detail & Related papers  (2022-11-16T20:28:49Z)
• Two quantum algorithms for communication between spacelike separated locations [0.7614628596146599]
  We argue that superluminal communication is possible through state discrimination in a higher-dimensional Hilbert space using ancilla qubits. We propose two quantum algorithms through state discrimantion for communication between two observers Alice and Bob.
  arXiv  Detail & Related papers  (2022-09-16T06:54:22Z)
• Quantum cryptography with classical communication: parallel remote state preparation for copy-protection, verification, and more [125.99533416395765]
  Many cryptographic primitives are two-party protocols, where one party, Bob, has full quantum computational capabilities, and the other party, Alice, is only required to send random BB84 states to Bob. We show how such protocols can generically be converted to ones where Alice is fully classical, assuming that Bob cannot efficiently solve the LWE problem. This means that all communication between (classical) Alice and (quantum) Bob is classical, yet they can still make use of cryptographic primitives that would be impossible if both parties were classical.
  arXiv  Detail & Related papers  (2022-01-31T18:56:31Z)
• Simultaneous Measurement and Entanglement [0.0]
  We show how LOCC allows Alice and Bob to distinguish between two product states optimally. We find that a LOCC is almost always more helpful than a Bell pair for distinguishing product states.
  arXiv  Detail & Related papers  (2022-01-25T23:11:29Z)
• Quantum secure direct communication with private dense coding using general preshared quantum state [59.99354397281036]
  We study secure direct communication by using a general preshared quantum state and a generalization of dense coding. For a practical application, we propose a concrete protocol and derive an upper bound of information leakage.
  arXiv  Detail & Related papers  (2021-12-30T16:12:07Z)
• About the description of physical reality of Bell's experiment [91.3755431537592]
  A hidden variables model complying with the simplest form of Local Realism was recently introduced. It reproduces Quantum Mechanics' predictions for an even ideally perfect Bell's experiment. A new type of quantum computer does not exist yet, not even in theory.
  arXiv  Detail & Related papers  (2021-09-06T15:55:13Z)
• Linear Gaussian Quantum State Smoothing: Understanding the optimal unravelings for Alice to estimate Bob's state [0.0]
  Quantum state smoothing is a technique to construct an estimate of the quantum state at a particular time. The effect of Bob's measurement choice on the effectiveness of Alice's smoothing has been studied in a number of recent papers. We develop a simple hypothesis that allows one to approximate the optimal measurement choice given Alice's measurement choice.
  arXiv  Detail & Related papers  (2020-08-31T04:04:50Z)
• Superadditivity of channel capacity through quantum fields [0.0]
  We study the scenario where a sender, Alice, causes information-carrying disturbances in a quantum field. We find that the channel capacity between Alice and a receiver, Bob, is enhanced by Bob placing detectors not only inside but also outside the causal future of Alice's encoding operation.
  arXiv  Detail & Related papers  (2020-02-11T00:53:34Z)

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.