Long-lived Matter Research Articles

A network-ready random-access qubits memory

Photonic qubits memories are essential ingredients of numerous quantum networking protocols. The ideal situation features quantum computing nodes that are efficiently connected to quantum communication channels via quantum interfaces. The nodes contain a set of long-lived matter qubits, the channels support the propagation of light qubits, and the interface couples light and matter qubits. Toward this vision, we here demonstrate a random-access multi-qubit write-read memory for photons using two rubidium atoms coupled to the same mode of an optical cavity, a setup that is known to feature quantum computing capabilities. We test the memory with more than ten independent photonic qubits, observe no noticeable cross-talk, and find no need for re-initialization even after ten write-read attempts. The combined write-read efficiency is 26% and the coherence time approaches 1 ms. With these features, the node constitutes a promising building block for a quantum repeater and ultimately a quantum internet.

High dimensional quantum entanglement

The phenomenon of quantum entanglement was initially introduced by Einstein and co-workers in their famous EPR paper when questioning the completeness of quantum theory, while the expression “entanglement” was soon after coined by Schrodinger. From an intriguing and fascinating aspect of quantum theory, entanglement has become in the last decades an invaluable resource for the emerging areas of quantum information and quantum technologies. Fundamental tests of quantum mechanics as well as first applications were, and are, largely based on the two orthogonal polarisation states of light. This well-developed standard approach of quantum optics turns out to be inadequate when confronted by the practical implementation of quantum technologies. Here the imperative is towards faster processing of ever increasing quantities of data, with opportunities provided by employing multi-dimensional and multi-modal quantum entanglement. The generation of entanglement and quantum correlations in high dimensional Hilbert spaces opens the way to a breakthrough in the information capacity of QIPC protocols, and provides a fundamental resource for quantum metrology and quantum imaging. In this context, light plays a fundamental role as the natural carrier of information over large distances and between logic elements within a processor. The longlived matter degrees of freedom instead enable the storage

Long-lived matter wave Bloch oscillations and dynamical localization by time-dependent nonlinearity management

We introduce a new method to achieve long-lived Bloch oscillations and dynamical localization of matter wave gap solitons in optical lattices. The method is based on the time-dependent modulations of the nonlinearity which can be experimentally implemented by means of the Feshbach resonance technique. In particular, we show that the width of the wavepacket is preserved if the time modulations of the nonlinearity are taken proportional to the curvature of the linear band spectrum which for most typical experimental settings are well approximated by harmonic time modulations of proper frequencies.

Multiplicative conservation of baryon number and baryogenesis

In the canonical seesaw mechanism of neutrino mass, lepton number is only multiplicatively conserved, which enables the important phenomenon of leptogenesis to occur, as an attractive explanation of the present baryon asymmetry of the Universe. A parallel possibility, hitherto unrecognized, also holds for baryon number and baryogenesis. This new idea is shown to be naturally realized in the context of a known supersymmetric string-inspired extension of the Standard Model, based on E6 particle content, and having an extra U(1)N gauge symmetry. Within this framework, two-loop radiative neutrino masses are also possible, together with a new form of very long-lived matter.

Amplification of light and atoms in a bose-einstein condensate

A Bose-Einstein condensate illuminated by a single off-resonant laser beam ("dressed condensate") shows a high gain for matter waves and light. We have characterized the optical and atom-optical properties of the dressed condensate by injecting light or atoms, illuminating the key role of long-lived matter wave gratings produced by the condensate at rest and recoiling atoms. The narrow bandwidth for optical gain gave rise to an extremely slow group velocity of an amplified light pulse ( approximately 1 m/s).