Single Photon Transistor Mediated by Inter-State Rydberg Interaction (1404.2876v2)

Abstract: We report on the realization of an all-optical transistor by mapping gate and source photons into strongly interacting Rydberg excitations with different principal quantum numbers in an ultracold atomic ensemble. We obtain a record switch contrast of 40 % for a coherent gate input with mean photon number one and demonstrate attenuation of source transmission by over 10 photons with a single gate photon. We use our optical transistor to demonstrate the nondestructive detection of a single Rydberg atom with a fidelity of 0.72(4).

• The paper realizes a single-photon transistor using inter-state Rydberg interactions, achieving a switch contrast of ~40% and gain greater than 10.
• It employs electromagnetically induced transparency in an ultracold atomic ensemble to map photons onto Rydberg excitations and induce strong optical nonlinearities.
• The work enables nondestructive, high-fidelity detection of Rydberg atoms, marking a significant step toward scalable quantum computing technologies.

Single Photon Transistor Mediated by Inter-State Rydberg Interaction

The paper introduces a significant advancement in optical quantum technology with the realization of an all-optical transistor. This design utilizes inter-state Rydberg interactions in an ultracold atomic ensemble, achieving substantial switch contrast and gain surpassing previous efforts outside of cavity QED systems.

Overview

The paper demonstrates the use of Rydberg states with varying principal quantum numbers to achieve strong photon-photon interaction via electromagnetically induced transparency (EIT). Through this approach, the authors successfully create a single-photon transistor, where one gate photon significantly alters the transmission of multiple source photons. The reported switch contrast is approximately 40% for a coherent gate input with an average of one photon, and the setup has the ability to attenuate source transmission by over ten photons with just a single gate photon. Furthermore, the authors illustrate the transistor's capability for nondestructive detection of individual Rydberg atoms, achieving a notable detection fidelity of 0.72.

Technical Implementation

The experimental setup involves mapping photons onto Rydberg states, where interactions between these states produce the necessary optical nonlinearities for transistor operation. This is achieved by employing a novel free-space design, separating gate and source photons spatially and spectrally to prevent cross-talk, and exploiting the strong interaction between Rydberg excitations.

The optical transistor operates by storing photons in the form of Rydberg excitations and monitoring the effective blockade on source photon transmission. The gate and source beams, tightly focused and counter-propagating through the atomic cloud, couple to specific Rydberg states, inducing a blockade effect that hinders the transmission of source photons in proximity to gate excitations, demonstrating the transistor's amplification capabilities.

Results and Implications

Key results include achieving a gain ($G$) greater than 10, surpassing prior non-cavity-based attempts. The authors identify challenges such as the self-blockade of source photons, which limits further gain enhancement. Significant future improvements could involve optimizing the geometry of the atomic cloud and exploiting alternative interaction channels, such as F\"orster resonances, to extend the range and efficacy of the transistor.

The practical implications of this work are vast. The successful implementation of a Rydberg-based single-photon transistor represents a critical step forward for quantum computing and information processing, especially in free-space and potentially integratable systems. The researchers highlight its utility in nondestructive atom detection, paving the way for high-fidelity, real-time monitoring of Rydberg atoms—an essential capability for future quantum technologies.

Theoretical and Future Perspectives

Theoretically, this demonstration underlines the power of Rydberg interactions for enabling strong photon-photon interactions without the need for cavities, highlighting a path towards more scalable and accessible quantum devices. The realization of retrieval mechanisms for gate photons remains a crucial next step, with the potential to unlock new classes of multi-photon quantum operations and enhance the applicability of non-classical light states in quantum communication protocols.

This work on coupling discrete optical channels with atomic states lays the groundwork for extensive exploration into two-photon gates and further manipulation of photon states using Rydberg polaritons. This could drive forward developments in quantum optics, enhancing capabilities in both fundamental research and burgeoning quantum technologies. The field can expect continued progress in achieving ever more functional and efficient optical transistors, intimately connected to the broader evolution of quantum information science.