Quantum Optical Communication in the presence of strong attenuation
noise
- URL: http://arxiv.org/abs/2204.13129v3
- Date: Mon, 24 Oct 2022 21:34:29 GMT
- Title: Quantum Optical Communication in the presence of strong attenuation
noise
- Authors: Francesco Anna Mele, Ludovico Lami, Vittorio Giovannetti
- Abstract summary: We show an even stronger version of D-HQCOM in the context of entanglement-assisted classical communication.
We provide a fully consistent protocol to activate the phenomena of D-HQCOM without directly accessing the environment state.
Our results may offer a concrete scheme to communicate across arbitrarily long optical fibres, without using quantum repeaters.
- Score: 8.808993671472349
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Is quantum communication possible over an optical fibre with transmissivity
$\lambda\leq 1/2$ ? The answer is well known to be negative if the environment
with which the incoming signal interacts is initialised in a thermal state.
However, in [PRL 125:110504, 2020] the quantum capacity was found to be always
bounded away from zero for all $\lambda>0$, a phenomenon dubbed "die-hard
quantum communication" (D-HQCOM), provided that the initial environment state
can be chosen appropriately (depending on $\lambda$). Here we show an even
stronger version of D-HQCOM in the context of entanglement-assisted classical
communication: entanglement assistance and control of the environment enable
communication with performance at least equal to that of the ideal case of
absence of noise, even if $\lambda>0$ is arbitrarily small. These two phenomena
of D-HQCOM have technological potential provided that we are able to control
the environment. How can we achieve this? Our second main result answers this
question. Here we provide a fully consistent protocol to activate the phenomena
of D-HQCOM without directly accessing the environment state. This is done by
sending over the channel "trigger signals", i.e. signals which do not encode
information, prior to the actual communication, with the goal of modifying the
environment in an advantageous way. This is possible thanks to the memory
effects which arise when the sender feeds signals separated by a sufficiently
short temporal interval. Our results may offer a concrete scheme to communicate
across arbitrarily long optical fibres, without using quantum repeaters. As a
by-product of our analysis, we derive a simple Kraus representation of the
thermal attenuator exploiting the associated Lindblad master equation.
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