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Exponentially Improved Quantum memory

Project description

Boosting interference suppresses light scattering in efficient quantum memory devices

Quantum memory is an interface between light and matter (atoms) based on the storage and retrieval of photonic quantum information or the quantum state of a photon. An overarching goal in quantum optics is to enhance the efficiency and control of interactions between photons and atomic media. Spontaneous emission in which photons are absorbed by atoms and then scattered in undesirable ways is a major challenge. Selective radiance is a phenomenon recently described which enables significant suppression of scattering through strong interference in emission between atoms. The EU-funded ExIQ project is evaluating this theoretical phenomenon experimentally with the goal of demonstrating quantum memory performance with a very small margin of error, supporting the development of future quantum networks.


We plan to demonstrate a new approach towards quantum memories based on a theoretical proposal which is centered around the phenomenon of selective radiance. Selective radiance occurs when the distance between emitters around a waveguide is smaller than the wavelength of the emitters. In this case destructive interference suppresses light scattering into all modes except the forward propagating target mode. This drastically reduces photon losses and increases the efficiency of the quantum memory operation. The error rate of such a new type of quantum memory scales with the optical depth (OD) as exp(-OD) in contrast to the previously established 1/OD. We plan to implement this new scheme with atomic emitters coupled to a nanofiber. Nanofiber based atom-light interfaces are versatile and scalable platforms which allow to precisely study these fundamental quantum effects and at the same time allow for easy integration into fiber based applications. The effect of selective radiance depends upon a lattice with a period smaller than the emitter wavelength. This will be achieved through an appropriate new choice of the laser wavelengths used in the optical trapping scheme. For best memory performance all lattice sites need to be filled. To realize this we use a collisional blockade effect in a Lambda-enhanced gray molasses cooling which ejects one atom every time two or more atoms are present at a lattice site. To optimize the quantum memory performance we will perform an in-depth study of the phenomenon of selective radiance by analyzing the transmission spectrum, the scattering into free space and by ring-down measurements. In the last step we will demonstrate the quantum memory performance and the exponential scaling with OD. The successful demonstration of this type of quantum memory is an important steps towards large distance distribution of quantum information and paves the way for future quantum networks.


Net EU contribution
€ 162 806,40
10117 Berlin

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Berlin Berlin Berlin
Activity type
Higher or Secondary Education Establishments
Total cost
€ 162 806,40