New Protocol to Store and Release Single Photon in Embedded Eigenstate

Quantum computers hold the potential for a new age of studies where the time required to achieve new technologies and lifesaving drugs will be considerably reduced. These computers use light particles, or photons, rather than electrons to transmit and process information.

The ASRC photonics team’s work could facilitate a new approach to capturing and preserving photons, speeding the development of quantum computers. Their calculations suggest that it is possible for a pair of photons to impinge on a cavity-atom coupled system, and that atomic nonlinearity will allow one photon to be perfectly trapped and preserved in the system while the other is re-emitted. (Image credit: Getty Images)

Photons are potential candidates for quantum computation since they have the ability to travel over long distances without any information loss. However, upon being stored in matter, they turn delicate and vulnerable to decoherence.

At present, a new protocol has been created by scientists with the Photonics Initiative at the Advanced Science Research Center (ASRC) at The Graduate Center, CUNY for the storage and release of a single photon in an embedded eigenstate, which is a quantum state virtually unaffected by decoherence and loss. The innovative protocol has been described in the latest issue of Optica. The aim of creating the protocol is to progress quantum computers development.

The goal is to store and release single photons on demand by simultaneously ensuring the stability of data. Our work demonstrates that is possible to confine and preserve a single photon in an open cavity and have it remain there until it’s prompted by another photon to continue propagating.

Andrea Alù, Founding Director, ASRC Photonics Initiative

Alù is also Einstein Professor of Physics at The Graduate Center.

The researchers developed their theory by using quantum electrodynamics methods. They studied a system formed of an atom and a cavity, where the cavity is partially open and hence would, in general, allow light entrapped within the system to escape out and be lost rapidly. However, they demonstrated that under specific conditions, destructive interference phenomena can eliminate leakage and enable a single photon to be indefinitely hosted in the system.

Although this embedded eigenstate could be very useful to store information without degradation, the closed nature of this protected state also forms a barrier to exterior stimuli. This makes it difficult to inject single photons into the system. The researchers could solve this drawback by exciting the system simultaneously with two or more photons.

We proposed a system that acts as a closed box when excited by a single photon, but it opens up very efficiently when we hit it with two or more photons. Our theory shows that two photons can be efficiently injected into the closed system. After that, one photon will be lost and the other will be trapped when the system closes. The stored photon has the potential to be preserved in the system indefinitely.

Michele Cotrufo, Postdoctoral Fellow, ASRC Photonics Initiative

Cotrufo is also the first author of the paper.

In realistic systems, further imperfections would hinder ideal confinement of photons; however, the calculations of the researchers revealed that their protocol performs better than earlier solutions based on a single cavity.

The team also demonstrated that it is possible to release the stored excited photon later on demand by sending a second pulse of photons.

The study outcomes have the potential to overcome crucial challenges to quantum computing, such as the on-demand creation of entangled photonic states and quantum memories. Currently, the researchers are exploring paths to experimental verification of their theoretical study.

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