We present an experiment where a reconfigurable photonic processor fabricated in glass by femtosecond laser micromachining is used for the generation of four-photons GHZ entangled states, with high efficiency and fidelity. The chip is used in synergy with a bright and quasi-deterministic source of single photons based on semiconductor quantum dot. The very efficient interfacing of these two platforms is ensured by the excellent connectivity between glass photonic circuits and standard optical fibers. In addition, in order to benchmark the quality of the generated states, this processor is used to implement a quantum secret sharing protocol on chip.
Quantum computing aims at exploiting quantum phenomena to efficiently perform computations that are unfeasible even for the most powerful classical supercomputers. Among the promising technological approaches, photonic quantum computing offers the advantages of low decoherence, information processing with modest cryogenic requirements, and native integration with classical and quantum networks. To date, quantum computing demonstrations with light have implemented specific tasks with specialized hardware, notably Gaussian Boson Sampling which permitted quantum computational advantage to be reached. Here we report a first user-ready general-purpose quantum computing prototype based on single photons.
One of the strong potentials of photonic quantum computing consist in the possibility to leverage matured technologies, currently implemented in several industrial domains.
Integrated photonic, one of the most prominent, has already been implemented in proof of principle quantum computing platforms demonstrating its viability for high precision control of large number of qubits. Nevertheless, the tools required to generate, manipulate and detect single and entangled photons are not part of standard fabrication processes; such integrated elements still require extensive research work before integrated photonic circuit could be implemented in large scale systems.
We present quantum computing protocols and a dedicated hardware architecture that takes advantage of photonic modularity and integrated photonic circuit with simplified architectures.
Semiconductor quantum dots have emerged as excellent artificial atoms to both generate and manipulate quantum light. When embedded in cavities, they can generate single photons and entangled photons with unparalleled efficiency and high quantum purity. In this talk, I will discuss how such devices can be used to generate strings of many entangled photons. The method, leveraging the spin-selective optical transition in a charged quantum dot, leads to the generation of indistinguishable photons in linear cluster states or GHZ states at high rates, realizing an important milestone for scaling-up optical quantum technologies.
We present the latest developments carried on in Quandela, where solid-state based quantum light sources with increased performances and usability were realized, allowing for plug-and-play operation, portability and integration in commercial infrastructure.
Semiconductor quantum dots (QDs) are promising artificial atoms for quantum information processing: they can generate single photons flying quantum bits; they show single photon sensitivity promising to develop quantum gates and the spin of a carrier in a QD can be a quantum memory. The scalability of a quantum network requires efficient interfaces between stationary and flying quantum bits. In the last few years, our group has made important progresses in this direction using cavity quantum electrodynamics.
With a deterministic positioning of a single QD in a microcavity, we control the QD spontaneous emission on demand [1]. With such technique highly efficient single photon sources with brightness as large as 80% are demonstrated [2]. By minimizing the charge noise around the QD in a gated structure [3], we demonstrate the generation of fully indistinguishable photon. The source brightness is shown to exceed by one or two orders of magnitude the one of a parametric down-conversion source of same quality [4]. Symmetrically, these devices perform as excellent interfaces between a flying quantum bit and a stationary one, where coherent control of a quantum bit can be done when only few photons [5].
References
[1] A. Dousse, et al. , Phys. Rev. Lett. 101, 267404 (2008)
[2] O. Gazzano, et al. , Nature Communications 4, 1425 (2013)
[3] A. Nowak. et al., Nature Communications 5, 3240 (2014)
[4] N. Somaschi, et al. Nature Photonics 10.1038/nphoton.2016.23 (2016).
[5] V. Giesz, et al., Nature Communications doi:10.1038/ncomms11986 (2016)
Characteristic low-threshold polariton lasing of organic and inorganic microcavity systems can only be achieved with
efficient population of the lower polariton ground state. In this regard, the key role undertaken by vibronic replicas and
molecular phonon it has been shown experimentally and theoretically predicted by various works. We report here, direct
observation of critical enhancement of polariton population density in strongly coupled J-aggregate based organic
microcavities. The process highlighted in our study is manifested by discrete maxima of the angular-resolved
photoluminescence intensity and interpreted by the mediation of molecular vibrations quanta characteristic of the active
material. By measuring the reduced time scale of vibrations driven relaxation dynamics, manifested by sub 100fs buildup
times, we emphasized the efficiency of the mechanism to overcome losses channel in disordered J-aggregate systems.
Hence, the realization of amplified polariton population with improved relaxation rates paves the way for the observation
of low threshold lasing, primary step for developing room temperature organic laser sources and ultra-fast optoelectronic
devices with less fabrication complexity than their crystalline counterparts.
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