[Paper Review] Quantum Shockwave Communication

Aida Ahmadzadegan, Eduardo Martín-Martínez+1 more|arXiv (Cornell University)|Nov 26, 2018

Quantum Information and Cryptography1 references5 citations

TL;DR

This paper proposes a quantum shockwave communication scheme using pre-timed, entangled Unruh-DeWitt detectors to generate coherent shockwaves in a quantum field, enabling spatially shaped information flow independent of energy propagation. The key result is that entanglement among emitters enhances local energy density and channel capacity, with an optimal receiver coupling strength that maximizes information transfer by balancing signal sensitivity and noise.

ABSTRACT

We present a scheme to produce shockwaves in quantum fields by means of pretimed emitters. We find that by suitably pre-entangeling the emitters, the shockwave's energy density can be locally modulated and amplified. When the large amplitudes in such a shockwave are used for communication, the channel capacity depends not only on the signal-to-noise ratio but also on the effect that the entanglement of the emitters has on the correlations in the signal and in the quantum noise at the receiver. As a consequence, by choosing the entanglement of the emitters, the flow of information in the shockwave can be modulated and spatially shaped to some extent independently of the flow of energy. We also find that there exists a finite optimal strength of the coupling between the receiver and the quantum field which optimizes the channel capacity by optimizing the tradeoff between sensitivity to the signal and sensitivity to the coupling-induced quantum noise.

Motivation & Objective

• To explore whether quantum shockwaves in empty space can be engineered using pre-timed, spatially separated quantum emitters.
• To investigate how entanglement among emitters affects shockwave energy density and information-carrying capacity.
• To determine if information flow can be spatially shaped independently of energy flow in quantum shockwaves.
• To identify the optimal coupling strength between the receiver and the quantum field that maximizes channel capacity.
• To assess the feasibility of using such shockwaves for quantum communication and measurement applications.

Proposed method

• Modeling emitters as Unruh-DeWitt detectors coupled to a free scalar quantum field in 3+1D Minkowski spacetime.
• Using Dirac delta switching functions to enable non-perturbative, exact calculations of field interactions.
• Employing spatially localized smearing functions (spherical, radius 0.5) to avoid ultraviolet divergences in field coupling.
• Pre-entangling multiple emitters (Alices) to coherently generate shockwaves with modulated energy density.
• Analyzing the receiver’s excitation probability as a function of coupling strength to determine channel capacity.
• Using non-perturbative methods to compute the trade-off between signal sensitivity and noise from receiver-field coupling.

Experimental results

Research questions

• RQ1 Can shockwaves be generated in a quantum field in empty space using only pre-timed, non-superluminal emitters?
• RQ2 How does pre-entanglement among emitters affect the energy density and information-carrying capacity of the resulting shockwave?
• RQ3 To what extent can information flow be spatially shaped independently of energy flow in quantum shockwaves?
• RQ4 Is there an optimal coupling strength between the receiver and the quantum field that maximizes channel capacity?
• RQ5 Can entanglement among emitters enable nonclassical coding schemes for quantum communication?

Key findings

• Pre-entangling the emitters allows local modulation and amplification of the shockwave’s energy density, enabling spatial shaping of information flow.
• Information flow is sensitive to multi-partite entanglement, while energy flow depends only on bi-partite entanglement, enabling independent control.
• A finite optimal coupling strength exists between the receiver and the field, beyond which quantum noise dominates and channel capacity decreases.
• The optimal coupling strength is independent of the signal strength and the emitters’ coupling, suggesting a universal trade-off in receiver design.
• The channel capacity increases with emitter coupling and entanglement, but saturates due to noise at high coupling, confirming a non-monotonic optimization.
• The scheme generalizes to quantum MIMO systems and may enable superresolution quantum measurements via time-reversed operation.