Observations using interferometers provide sensitivity to features of images on angular scales much smaller than any single telescope, on the order of Δθ ∼ λ/b where b is the interferometric baseline. Present-day optical interferometers are essentially classical, interfering single photons with themselves. However, there is a new wave of interest in interferometry using multiple photons, whose mechanisms are inherently quantum mechanical, which offer the prospects of increased baselines and finer resolutions among other advantages. We will discuss recent ideas and results for quantum-assisted interferometry using the resource of entangled pairs, and specifically a two-photon amplitude technique aimed at improved precision in astrometry.
The goal of quantum communication is to transmit quantum states between distant sites. The key aspect to achieve this goal is the generation of entangled states over long distances. Such states can then be used to faithfully transfer classical and quantum states via quantum teleportation. This is an exciting new direction which establishes the fundamentals of a new quantum internet. The big challenge, however, is that the entanglement rates generated between two distant sites decreases exponentially with the length of the connecting channel. To overcome this difficulty, the new concepts of entanglement swapping, and quantum repeater operation are needed.
In this talk we will show our progress towards building a quantum network of many quantum devices capable of distributing entanglement over long distances connecting Stony Brook University and the Brookhaven National Laboratory on Long Island, New York. We will show how to produce photonic quantum entanglement in the laboratory and how to store it and distribute it by optically manipulating the properties of atomic clouds. Finally, we will discuss our recent experiments in which several quantum devices are already interconnected forming elementary quantum cryptographic and quantum repeater networks.
Prospects of using entangled quantum networks for quantum sensing was recorded at SPIE Photonics West held in San Francisco, California, United States 2022.
First-generation long-distance quantum repeater networks require quantum memories capable of interfacing with telecom photons to perform quantum-interference-mediated entanglement generation operations. The ability to demonstrate these interconnections using real-life fiber connections in a long-distance setting is paramount to realize a scalable quantum internet.
It has been recently suggested that optical interferometers may not require a phase-stable optical link between the stations if instead sources of quantum-mechanically entangled pairs could be provided to them, enabling extra- long baselines and benefiting numerous topics in astrophysics and cosmology. We developed a new variation of this idea, proposing that two photons from different sources could be interfered at two decoupled stations, requiring only a slow classical information link between them. We show that this approach could allow high- precision measurements of the relative astrometry of the two sources, with a basic calculation giving angular precision of 10 µas in a few hours’ observation of two bright stars. We also give requirements on the instrument for these observations, in particular on its temporal and spectral resolution. Finally, we discuss possible technologies for the instrument implementation and first proof-of-principle experiments.
We demonstrate a quantum communication protocol that enables frequency conversion of quantum optical information in an adiabatic way. The protocol is based on electromagnetically induced transparency in sustems with multiple excited levels. The proof-of-principle experiment is performed using the hyperfine levels of the rubidium D1 line.
We report characterization of EIT resonances in the D1 line of Rb 87 under various experimental conditions. The dependence of the EIT linewidth on the power of the control field investigated. Strictly linear behavior between the ground levels as the main source of decoherence. We therefore formulated a new theory assuming pure dephasing to be the main decoherence mechanism. We also performed experiments where we created additional decoherence mechanisms by means of a counter-propagating repumper field. This field caused the ground-state population exchange, thus reproducing conditions in which the original theory is valid.
We present an experimental study of decoherence of the ground energy levels of 87Rb atoms in vapor cells. We measure the decoherence of the ground state using three different methods: measuring the decay constant of the storage of light in atomic vapor, the decay rates of transient coherence oscillations of the ground state, and the width of the electromagnetically induced transparency resonances. The measurements showed decoherence rates on the scale of 104 s-1.
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