Proof-of-principle demonstration of compiled Shor's algorithm using a quantum dot single-photon source

Funding: National Natural Science Foundation of China (11575174, 11674308, 11704424, 11774326, 11874346); Chinese Academy of Sciences; National Key Research and Development Program of China.We report a proof-of-principle demonstration of Shor’s algorithm with photons generated by an on-demand semiconductor quantum dot single-photon source for the first time. A fully compiled version of Shor’s algorithm for factoring 15 has been accomplished with a significantly reduced resource requirement that employs the four-photon cluster state. Genuine multiparticle entanglement properties are confirmed to reveal the quantum character of the algorithm and circuit. The implementation realizes the Shor’s algorithm with deterministic photonic qubits, which opens new applications for cluster state beyond one-way quantum computing.Publisher PDFPeer reviewe

Eliminating temporal correlation in quantum-dot entangled photon source by quantum interference

Semiconductor quantum dots, as promising solid-state platform, have exhibited deterministic photon pair generation with high polarization entanglement f\textcompwordmark idelity for quantum information applications. However, due to temporal correlation from inherently cascaded emission, photon indistinguishability is limited, which restricts their potential scalability to multi-photon experiments. Here, by utilizing quantum interferences to decouple polarization entanglement from temporal correlation, we improve multi-photon entanglement f\textcompwordmark idelity from $(58.7\pm 2.2)\%$ to $(75.5\pm 2.0)\%$. Our work paves the way to realize scalable and high-quality multi-photon states from quantum dots

High-efficiency single-photon source above the loss-tolerant threshold for efficient linear optical quantum computing

Photon loss is the biggest enemy for scalable photonic quantum information processing. This problem can be tackled by using quantum error correction, provided that the overall photon loss is below a threshold of 1/3. However, all reported on-demand and indistinguishable single-photon sources still fall short of this threshold. Here, by using tailor shaped laser pulse excitation on a high-quantum efficiency single quantum dot deterministically coupled to a tunable open microcavity, we demonstrate a high-performance source with a single-photon purity of 0.9795(6), photon indistinguishability of 0.9856(13), and an overall system efficiency of 0.712(18), simultaneously. This source for the first time reaches the efficiency threshold for scalable photonic quantum computing. With this source, we further demonstrate 1.89(14) dB intensity squeezing, and consecutive 40-photon events with 1.67 mHz count rate

The LAMOST Survey of Background Quasars in the Vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the Commissioning Observations and the Pilot Surveys

We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the LAMOST during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available SDSS, KPNO 4 m telescope, XSTPS optical, and WISE near infrared photometric data. We present 509 new quasars discovered in a stripe of ~135 sq. deg from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey datasets, and also 17 new quasars discovered in an area of ~100 sq. deg that covers the central region and the southeastern halo of M31 in the 2010 commissioning datasets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62 and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5 and 18.0 respectively, of which 5, 20 and 75 are newly-discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the ISM/IGM in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.5 deg of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute PMs of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local Group.Comment: 26 pages, 6 figures, AJ accepte

Quantum Neuronal Sensing of Quantum Many-Body States on a 61-Qubit Programmable Superconducting Processor

Classifying many-body quantum states with distinct properties and phases of matter is one of the most fundamental tasks in quantum many-body physics. However, due to the exponential complexity that emerges from the enormous numbers of interacting particles, classifying large-scale quantum states has been extremely challenging for classical approaches. Here, we propose a new approach called quantum neuronal sensing. Utilizing a 61 qubit superconducting quantum processor, we show that our scheme can efficiently classify two different types of many-body phenomena: namely the ergodic and localized phases of matter. Our quantum neuronal sensing process allows us to extract the necessary information coming from the statistical characteristics of the eigenspectrum to distinguish these phases of matter by measuring only one qubit. Our work demonstrates the feasibility and scalability of quantum neuronal sensing for near-term quantum processors and opens new avenues for exploring quantum many-body phenomena in larger-scale systems.Comment: 7 pages, 3 figures in the main text, and 13 pages, 13 figures, and 1 table in supplementary material

Experimental quantum computational chemistry with optimised unitary coupled cluster ansatz

Simulation of quantum chemistry is one of the most promising applications of quantum computing. While recent experimental works have demonstrated the potential of solving electronic structures with variational quantum eigensolver (VQE), the implementations are either restricted to nonscalable (hardware efficient) or classically simulable (Hartree-Fock) ansatz, or limited to a few qubits with large errors for the more accurate unitary coupled cluster (UCC) ansatz. Here, integrating experimental and theoretical advancements of improved operations and dedicated algorithm optimisations, we demonstrate an implementation of VQE with UCC for H_2, LiH, F_2 from 4 to 12 qubits. Combining error mitigation, we produce high-precision results of the ground-state energy with error suppression by around two orders of magnitude. For the first time, we achieve chemical accuracy for H_2 at all bond distances and LiH at small bond distances in the experiment. Our work demonstrates a feasible path towards a scalable solution to electronic structure calculation, validating the key technological features and identifying future challenges for this goal.Comment: 8 pages, 4 figures in the main text, and 29 pages supplementary materials with 16 figure

The evaluation of risk for obstructive sleep apnea in patients with type 2 diabetes

Cilj istraživanja je procijeniti rizik za opstrukcijsku apneju tijekom spavanja (engl. Obstructive sleep apnea, OSA) u bolesnika sa šećernom bolešću tipa 2, s pomoću STOP upitnika (engl. Snoring, Tiredness, Observed, Pressure; STOP). S pomoću Epworthove ljestvice pospanosti (ESS) procijenjena je prekomjerna dnevna pospanost i ispitana povezanost pospanosti i rizika za OSA-u u bolesnika sa šećernom bolešću tipa 2. Dosadašnja istraživanja pokazala su da oštećena tolerancije glukoze i šećerna bolest tipa 2 predstavljaju čimbenik rizika za OSA-u, ali i da OSA predstavlja čimbenik rizika za šećernu bolest tipa 2. U našem istraživanju sudjelovala su 252 ispitanika sa šećernom bolešću tipa 2, koji su bili anketirani za vrijeme redovitih pregleda u Kliničkom bolničkom centru Split. Rezultati našeg istraživanja pokazali su da je 156 ispitanika (61,9%) imalo povećan rizik za OSA-u prema rezultatima STOP upitnika. Nadalje, ispitanici koji su imali povećani rizik u odnosu na ispitanike koji nisu imali rizik za OSA-u bili su stariji (65 vs. 61 godina, p < 0,05), imali viši indeks tjelesne mase (28,6 ± 5,1 vs. 26,5 ± 4,1, p < 0,001), veći opseg vrata (41,5 ± 4,7 vs. 39,6 ± 6,2, p < 0,009) i bili pospaniji prema rezultatima ESS (5,3 ± 3,1 vs. 3,9 ± 2,5, p < 0,001). Uz šećernu bolest, većina ispitanika imala je i pridružene bolesti: arterijska hipertenzija (46%), gastroezofagealna refluksna bolest (28%), depresija (10%) i astma (8%). OSA je dio širokoga spektra poremećaja disanja tijekom spavanja koja se dovodi u vezu s metaboličkim poremećajima poput šećerne bolesti tipa 2, a epidemiološki podaci o zastupljenosti OSA u Hrvatskoj su nedostatni. Ovo istraživanje ukazuje na potrebu provođenja probira za OSA u bolesnika sa šećernom bolešću tipa 2, koristeći STOP upitnik.The aim of this study was to evaluate the risk for obstructive sleep apnea (OSA) in patients with type 2 diabetes using the STOP questionnaire (Snoring, Tiredness, Observed, Pressure; STOP). Excessive daytime sleepiness was evaluated with the Epworth sleepiness scale (ESS). Previous studies support the idea that glucose intolerance and type 2 diabetes might represent risk factors for OSA, as well as the idea of OSA being the risk factor for type 2 diabetes. A total of 252 patients with type 2 diabetes were surveyed during the regular follow-up in the Regional Centre for Diabetes, Endocrinology and Metabolic Diseases of Split University Hospital. The results of our study indicate that 156 patients (61.9%) had increased risk for OSA according to STOP questionnaire score. In addition, those at high risk for OSA were older (65 vs. 61 years of age, p < 0.05), had higher body mass index (BMI, 28.6 ± 5.1 vs. 26.5 ± 4.1, p < 0.001), higher neck circumference (41.5 ± 4.7 vs. 39.6 ± 6.2, p < 0.009), and had excessive daytime sleepiness according to the ESS score (5.3 ± 3.1 vs. 3.9 ± 2.5, p < 0.001). Individuals with type 2 diabetes reported to have comorbidities, mainly hypertension (46%), gastroesophageal reflux disease (28%), depression (10%), and asthma (8%). Based on current evidence from literature, OSA could be related to clinical conditions such as diabetes and essential hypertension. More epidemiological data are needed to establish the prevalence of OSA in Croatian patients with type 2 diabetes. Our findings indicate the relevance of STOP questionnaire use as a screening tool for obstructive sleep apnea in patients with type 2 diabetes in Croatia