Abstract
In this paper, we study a general linear networked system that contains a tunable memory subsystem; that is, it is decoupled from an optical field for state transportation during the storage process, while it couples to the field during the writing or reading process. The input is given by a single photon state or a coherent state in a pulsed light field. We then completely and explicitly characterize the condition required on the pulse shape achieving the perfect state transfer from the light field to the memory subsystem. The key idea to obtain this result is the use of zero-dynamics principle, which in our case means that, for perfect state transfer, the output field during the writing process must be a vacuum. A useful interpretation of the result in terms of the transfer function is also given. Moreover, a four-node network composed of atomic ensembles is studied as an example, demonstrating how the input field state is transferred to the memory subsystem and what the input pulse shape to be engineered for perfect memory looks like.
Highlights
Quantum memory is, in a wide sense, a device that stores or freezes a quantum state both spatially and in time
Cannot be preserved, but only its (3, 4, 5) components can be. This means that the original field state ∣1ξ 〉F with s1 = s2 = 0 can be perfectly transferred and stored in the memory subsystem; the input pulse shape should be synthesized by multiplying the classical information (s3, s4, s5) with the basis functions (ν3(t), ν4(t), ν5(t) ), generating as a result ξ(t) = s3ν3(t) + s4 ν4(t) + s5ν5(t)
A numerical simulation will demonstrate how the input field state is transferred to the memory subsystem and what the input pulse shape to be engineered for perfect memory looks like
Summary
In a wide sense, a device that stores or freezes a quantum state both spatially and in time. As a principle, the output should be ‘zero’ during the writing and storage stages This simple zero-dynamics principle leads us to prove, very that a rising exponential function is a unique pulse shape achieving the perfect state transfer for general (and large-scale) linear passive networks. Based on this first main result, we give an explicit, simple and general procedure for designing the wave packet carrying an unknown state that is as a result perfectly absorbed in the memory subsystem.
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