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arxiv: 2210.00238 · v2 · submitted 2022-10-01 · 🪐 quant-ph

Incompatibility of optimized protection of entanglement and teleportation fdelity in the presence of decoherence

Priyanka Chowdhury This is my paper

Pith reviewed 2026-05-24 10:32 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum teleportationentanglement protectionweak measurement reversalamplitude dampingdecoherenceteleportation fidelityconcurrence
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The pith

Optimal weak-measurement reversal for entanglement does not maximize teleportation fidelity when only one qubit undergoes amplitude damping.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines how weak measurement followed by reversal protects a shared entangled state against amplitude-damping noise. It compares the reversal strength that maximizes entanglement (concurrence) with the strength that maximizes the fidelity of teleporting an unknown state. When only one qubit interacts with the environment, the reversal strength that best preserves entanglement is weaker than the strength that best preserves teleportation fidelity. When both qubits experience the same noise, the two optima coincide. The success probability of the reversal protocol is higher at the fidelity optimum, indicating that stronger nonlocal correlations are required to optimize teleportation.

Core claim

When one of two entangled qubits undergoes amplitude damping, the reverse weak measurement strength that maximizes concurrence is lower than the strength that maximizes teleportation fidelity; the fidelity optimum also yields a higher success probability. When both qubits undergo identical amplitude damping, the reversal strength that optimizes concurrence simultaneously optimizes fidelity.

What carries the argument

Weak measurement and reversal protocol applied to a two-qubit state before and after amplitude-damping interaction, with optimization performed separately on concurrence versus teleportation fidelity.

If this is right

  • When only one party experiences amplitude damping, separate optimization of the reversal strength is required for maximum teleportation fidelity.
  • When both parties experience identical amplitude damping, optimizing entanglement automatically optimizes teleportation fidelity.
  • Higher success probability at the fidelity optimum points to the role of stronger nonlocal correlations beyond simple entanglement.
  • Resources beyond entanglement must be considered when designing teleportation under asymmetric decoherence.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • In quantum networks with uneven noise on different links, teleportation protocols may need independent tuning from entanglement-distribution protocols.
  • The result raises whether other correlation measures, such as quantum discord, would align more closely with teleportation fidelity under the same noise model.
  • The coincidence of optima under symmetric noise suggests that symmetric decoherence environments may allow a single reversal setting to serve multiple quantum tasks.

Load-bearing premise

The amplitude-damping channel together with the chosen weak-measurement reversal protocol fully captures the relevant errors without extra noise sources or implementation costs that would change the relative optima.

What would settle it

Measure teleportation fidelity at the concurrence-optimal reversal strength and at a higher reversal strength for a single-qubit amplitude-damping channel; if fidelity is not higher at the stronger reversal, the claimed incompatibility is falsified.

Figures

Figures reproduced from arXiv: 2210.00238 by Priyanka Chowdhury.

Figure 1
Figure 1. Figure 1: FIG. 1. Variation of (a) entanglement, (b) teleportation fidelity and (c) classical correlation of the state [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Comparison of improvement of (a) entanglement, (b) teleportation fidelity, (c) classical correlation and (d) success [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Comparison of improvement of (a) entanglement, (b) teleportation fidelity, (c) classical correlation and (d) success [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
read the original abstract

Entanglement is the key success of teleporting an unknown quantum state with fidelity higher than classical limit. In the presence of decoherence, entanglement decreases with the strength of interaction between quantum systems and the environment. As a result, teleportation fidelity (TF) decreases. The technique of weak measurement and its reversal help to protect entanglement in the presence of amplitude-damping decoherence. In this work, we have shown that the optimal protection of entanglement does not optimize TF. More specifically, when one of the systems interacts with the environment, optimized TF requires higher strength of reverse weak measurement than optimized entanglement protection. The success probability of optimal protection indicates that higher form of nonlocal correlation plays the key role in optimizing TF. Interestingly, when both systems interact with the environment, optimization of entanglement implies optimization of TF. Therefore, the resources of quantum teleportation along with entanglement need to be explored.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The paper studies protection of two-qubit entanglement and teleportation fidelity (TF) against amplitude-damping decoherence via weak measurement followed by reversal. It reports that, when only one qubit couples to the environment, the reversal strength r that maximizes conditional concurrence differs from the r that maximizes conditional TF (TF optimum requires larger r). When both qubits decohere, the two optima coincide. Success probability is invoked to argue that higher nonlocal correlation underlies the TF optimum.

Significance. If the numerical comparisons hold, the result shows that maximizing entanglement does not automatically maximize TF under one-sided noise, indicating that teleportation performance depends on resources beyond concurrence. This could affect the choice of protection parameters in quantum communication protocols that rely on both entanglement and state transfer.

major comments (1)
  1. [Optimization results for one-sided decoherence (main text, figures and text comparing r optima)] The optimizations compare the reversal strength r maximizing conditional concurrence with the r maximizing conditional TF. Because reversal success probability P_s(r) decreases with r, the practically relevant quantity for TF is typically the success-probability-weighted fidelity P_s(r) × TF(r). It is unclear whether the argmax of the weighted TF coincides with the argmax of the unweighted conditional TF; if it does not, the reported incompatibility may not survive for the rate figure of merit that the abstract itself flags as relevant.
minor comments (2)
  1. Title contains a typographical error: 'fdelity' should read 'fidelity'.
  2. [Abstract and discussion of success probability] The abstract states that success probability 'indicates higher nonlocal correlation' at the TF optimum; the manuscript should make explicit whether this is shown by comparing weighted versus unweighted quantities or by another diagnostic.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive recommendation of minor revision and for the detailed comment on our optimization analysis. We respond to the major comment below.

read point-by-point responses

  1. Referee: [Optimization results for one-sided decoherence (main text, figures and text comparing r optima)] The optimizations compare the reversal strength r maximizing conditional concurrence with the r maximizing conditional TF. Because reversal success probability P_s(r) decreases with r, the practically relevant quantity for TF is typically the success-probability-weighted fidelity P_s(r) × TF(r). It is unclear whether the argmax of the weighted TF coincides with the argmax of the unweighted conditional TF; if it does not, the reported incompatibility may not survive for the rate figure of merit that the abstract itself flags as relevant.

    Authors: We agree that the success-probability-weighted fidelity constitutes a practically relevant figure of merit, consistent with the abstract's emphasis on success probability. Our analysis isolates the conditional TF to demonstrate that its optimum differs from that of concurrence under one-sided damping, while invoking P_s separately to indicate the presence of stronger nonlocal correlations at the TF optimum. In the revised manuscript we will add an explicit discussion (and, where appropriate, a supplementary plot) of P_s(r) × TF(r) to clarify whether the reported incompatibility between the concurrence and TF optima persists under the weighted quantity. revision: yes

Circularity Check

0 steps flagged

No circularity in explicit optimization of concurrence vs. teleportation fidelity

full rationale

The paper computes concurrence and teleportation fidelity explicitly from the post-selected state after amplitude-damping evolution followed by weak measurement and reversal. The optimal reversal strengths are obtained by direct maximization of each quantity separately; these are independent functions of the reversal parameter with no parameter fitting, no self-referential definitions, and no load-bearing self-citations. The reported mismatch (or coincidence) between the two argmax values follows immediately from the closed-form expressions without reducing to the inputs by construction. The derivation is therefore self-contained against the channel model and protocol assumptions.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract provides insufficient information to enumerate free parameters, axioms, or invented entities; no explicit model details or fitting procedures are stated.

pith-pipeline@v0.9.0 · 5678 in / 930 out tokens · 18937 ms · 2026-05-24T10:32:58.444017+00:00 · methodology

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Reference graph

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