In the quest to realize a scalable quantum network, semiconductor quantum dots (QDs) offer distinct advantages, including high single-photon efficiency and indistinguishability, high repetition rate (tens of gigahertz with Purcell enhancement), interconnectivity with spin qubits, and a scalable on-chip platform. However, in the past two decades, the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%, and the distances were limited from a few meters to kilometers. Here, we report quantum interference between two single photons from independent QDs separated by a 302 km optical fiber. The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities. Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band. The observed interference visibility is 0.67 ± 0.02 (0.93 ± 0.04) without (with) temporal filtering. Feasible improvements can further extend the distance to ∼600 km. Our work represents a key step to long-distance solid-state quantum networks.
The quantum internet will give us an infrastructure able to distribute and process quantum information on a planetary scale. The core of that internet will be formed from quantum error corrected links able to distribute information over large distances all while maintaining their coherence for long periods of time. However, many of the applications at the edge of such networks may rely on raw unencoded data – not protected by error correcting codes due to the nature of how it was generated. In this presentation, we will describe an experiment in which quantum information encoded on a physical qubit can be teleported into an error-corrected logical qubit. Our demonstration shows how one can get information into and out of quantum processors and tomorrows large-scale quantum networks.
Quantum walks are a well-known powerful technique to perform quantum search algorithms, quantum simulations, and universal quantum computation. They have been extensively explored in the optical regime. In our work we have realized an 8x8 two-dimensional square superconducting qubit array with 62 functional qubits. We have used this processor to demonstrate high fidelity multi-particle quantum walks. The programmability of our processor also allows us to implement a Mach-Zehnder interferometer where quantum walkers can coherently traverse both paths of the interferometer before interfering and exiting it. Our work shows an alternate approach for information processing on these NISQ processors.
We realize quantum computational advantage in a Gaussian Boson Sampling (GBS) experiment. We inject 25 two mode squeezed states into a 100-mode ultralow-loss interferometer with full connectivity and random matrix. We rule out thermal states, distinguishable photons, and uniform distribution hypotheses. This GBS machine can sample 14 orders of magnitude faster than classical supercomputer.
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