Weizmann Institute Scientists Develop Universal Approach for Quantum Interfaces

Researchers from the Weizmann Institute of Science in Israel have developed a universal approach for analyzing quantum interfaces composed of atom collections interacting with paraxial light. The method, detailed in their paper “Universal Approach for Quantum Interfaces with Atomic Arrays”, maps atom-photon interfaces onto a one-dimensional model of light scattering, characterized by a reflectivity parameter r0. This parameter universally determines the efficiency of the quantum interface, which can be significantly improved by designing a photon mode that matches the collective-dipole eigenmode of the atoms. The approach applies to various platforms, including finite-size atomic arrays and partially filled arrays.

What is the Universal Approach for Quantum Interfaces with Atomic Arrays?

The research paper titled “Universal Approach for Quantum Interfaces with Atomic Arrays” was authored by Yakov Solomons, Roni BenMaimon, and Ephraim Shahmoon from the Department of Chemical Biological Physics at the Weizmann Institute of Science in Israel. The paper was received on 9 February 2023, revised on 2 December 2023, accepted on 2 April 2024, and published on 7 May 2024. The paper presents a general framework for analyzing two-sided quantum interfaces composed of collections of atoms interacting with paraxial light.

The researchers’ approach is based on mapping collective atom-photon interfaces onto a generic one-dimensional model of light scattering, characterized by a reflectivity parameter r0. This approach has two key practical advantages. Firstly, the efficiency of the quantum interface in performing various quantum tasks, such as quantum memory or entanglement generation, is universally given by r0 and is hence reduced to a measurement or classical calculation of reflectivity. Secondly, the efficiency can be greatly enhanced by a properly designed photon mode that spatially matches a collective-dipole eigenmode of the atoms.

How Does This Approach Apply to Realistic Cases?

The researchers demonstrate their approach for realistic cases of finite-size atomic arrays, partially filled arrays, and circular arrays. This provides a unified approach for treating collective light-matter coupling in various platforms such as optical lattices and optical tweezers.

Quantum optical platforms based on the manipulation of atoms and photons play an essential role in the exploration of quantum science and technology. Of crucial importance is the ability to establish an interface between photons and atoms. Such an interface allows one to benefit from the low-loss propagation of photons combined with the quantum coherence or nonlinearity of atoms with applications ranging from quantum memories and information to many-body physics.

What is the Role of Reflectivity in Quantum Interfaces?

The efficiency of the interface is characterized by the ratio between the emission rate of the atomic degree of freedom to the target mode and that to the rest of the undesired modes. This ratio depends on the specific realization for an ensemble of atoms trapped in free space or along a waveguide. It is typically given by the so-called optical depth (OD), whereas for atoms trapped inside a cavity, this ratio is often identical to the cooperativity parameter.

The researchers found that the reflectivity of the target mode, given by r0, fully characterizes atom-photon coupling. In particular, r0 is equal to the efficiency of energy conversion between the dipole and the target mode and hence emerges as a universal figure of merit of quantum tasks. This is demonstrated for efficiencies of quantum memory and entanglement generation analyzed for corresponding linear and nonlinear variants of the model.

How Can This Approach Be Enhanced?

The researchers show how the reflectivity and hence the efficiency can be greatly enhanced by a properly designed photon mode that spatially matches the collective eigenmodes of the array structure. This means that by carefully designing the photon mode, the efficiency of the quantum interface can be significantly improved.

In conclusion, the research paper presents a universal approach for analyzing two-sided quantum interfaces composed of collections of atoms interacting with paraxial light. The approach is based on mapping collective atom-photon interfaces onto a generic one-dimensional model of light scattering, characterized by a reflectivity parameter r0. The researchers demonstrate their approach for realistic cases of finite-size atomic arrays, partially filled arrays, and circular arrays, providing a unified approach for treating collective light-matter coupling in various platforms. The efficiency of the quantum interface is universally given by r0 and can be greatly enhanced by a properly designed photon mode that spatially matches a collective-dipole eigenmode of the atoms.