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Author: Subject: Claimed quantum computer breakthough
leau
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[*] posted on 28-1-2022 at 09:53


Quantum spin liquids in a square lattice subject to an Abelian flux and its experimental observation in cold atoms or photonic systems

Fadi Sun and Jinwu Ye

https://arxiv.org/abs/2005.04695

We report that a possible Z 2 quantum spin liquid (QSL) can be observed in a new class of frustrated system: spinor bosons subject to a π flux in a square lattice. We construct a new class of Ginsburg-Landau (GL) type of effective action to classify possible quantum or topological phases at any coupling strengths. It can be used to reproduce the frustrated SF with the 4 sublattice 90 ◦coplanar spin structure plus its excitations in the weak coupling limit and the FM Mott plus its excitations in the strong coupling limit achieved in our previous work. It also establishes deep and intrinsic connections between the GL effective action and the order from quantum disorder (OFQD) phenomena in the weak coupling limit. Most importantly, it predicts two possible new phases at intermediate couplings: a FM SF phase or a frustrated magnetic Mott phase. We argue that the latter one is more likely and melts into a Z 2 quantum spin liquid (QSL) phase. If the heating issue can be under a reasonable control at intermediate couplings U/t ∼ 1, the topological order of thhe Z 2 QSL maybe uniquely probed by the current cold atom or photonic experimental techniques


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[*] posted on 29-1-2022 at 05:33


Preparing for Quantum-Safe Cryptography
An NCSC whitepaper about mitigating the threat to cryptography from development in Quantum Computing.

https://www.ncsc.gov.uk/whitepaper/preparing-for-quantum-saf...


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[*] posted on 30-1-2022 at 06:32


Quantum phases of Rydberg atoms on a kagome lattice

Rhine Samajdar, Wen Wei Ho, Hannes Pichler , Mikhail D. Lukin, and Subir Sachdev

Proc Natl Acad Sci. 2021 Jan 26;118(4):e2015785118.
doi: 10.1073/pnas.2015785118.

We analyze the zero-temperature phases of an array of neutral atoms on the kagome lattice, interacting via laser excitation to atomic Rydberg states. Density-matrix renormalization group calculations reveal the presence of a wide variety of complex solid phases with broken lattice symmetries. In addition, we identify a regime with dense Rydberg excitations that has a large entanglement entropy and no local order parameter associated with lattice symmetries. From a mapping to the triangular lattice quantum dimer model, and theories of quantum phase transitions out of the proximate solid phases, we argue that this regime could contain one or more phases with topological order. Our results provide the foundation for theoretical and experimental explorations of crystalline and liquid states using programmable quantum simulators based on Rydberg atom arrays.


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[*] posted on 31-1-2022 at 09:49


Evidence for a Z 2 topological ordered quantum spin liquid in a kagome-lattice antiferromagnet

Yuan Wei, Zili Feng, Wiebke Lohstroh, D. H. Yu, Clarina dela Cruz, Wei Yi, Z. F. Ding, J. Zhang, Cheng Tan, Lei Shu, Yan-Cheng Wang, Han-Qing Wu, Jianlin Luo, Jia-Wei Mei, Zi Yang Meng, Youguo Shi and Shiliang Li

https://arxiv.org/abs/1710.02991v1

A quantum spin liquid with a Z 2 topological order has long been thought to be important for the application of quantum computing and may be related to high-temperature superconductivity. While a two-dimensional kagome antiferromagnet may host such a state, strong experimental evidences are still lacking]. Here we show that the spin excitations from the kagome planes in magnetically ordered Cu 4 (OD) 6 FBr and non-magnetically ordered Cu 3 Zn(OD) 6 FBr are similarly gapped although the content of inter-kagome-layer Cu 2+ ions changes dramatically. This suthat the spin triplet gap and continuum of the intrinsic kagome antiferromagnet are robust against the interlayer magnetic impurities. Our results show that the ground state of Cu 3 Zn(OD) 6 FBr is a gapped quantum spin liquid with Z 2 topological order.


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[*] posted on 1-2-2022 at 11:18


Scheme for the generation of hybrid entanglement between time-bin and wavelike encodings

Élie Gouzien, Floriane Brunel, Sébastien Tanzilli, and Virginia D’Auria

DOI : 10.1103/PhysRevA.102.012603
https://arxiv.org/abs/2002.04450
HAL Id : hal-02474883, version 2

We propose a scheme for the generation of hybrid states entangling a single-photon time-bin qubit with a coherent-state qubit encoded on phases. Compared to other reported solutions, time-bin encoding makes hybrid entanglement particularly well adapted to applications involving long-distance propagation in optical fibers. This makes our proposal a promising resource for future out-of-the-laboratory quantum communication. In this perspective, we analyze our scheme by taking into account realistic experimental resources and discuss the impact of their imperfections on the quality of the obtained hybrid state


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[*] posted on 2-2-2022 at 08:37


A hybrid quantum repeater for qudits

Marcel Bergmann and Peter van Loock

https://arxiv.org/abs/1708.09322 Phys. Rev. A 99, 032349

We present a "hybrid quantum repeater" protocol for the long-distance distribution of atomic entangled states beyond qubits. In our scheme, imperfect noisy entangled pairs of two qudits, i.e., two discrete-variable d-level systems, each of, in principle, arbitrary dimension d, are initially shared between the intermediate stations of the channel. This is achieved via local, sufficiently strong light-matter interactions, involving optical coherent states and their transmission after these interactions, and optical measurements on the transmitted field modes, especially (but not restricted to) efficient continuous-variable homodyne detections ("hybrid" here refers to the simultaneous exploitation of discrete and continuous variable degrees of freedom for the local processing and storage of entangled states as well as their non-local distribution, respectively). For qutrits we quantify the light-matter entanglement that can be effectively shared through an elementary lossy channel, and for a repeater spacing of up to 10 km we show that the realistic (lossy) qutrit entanglement is even larger than any ideal (loss-free) qubit entanglement. After including qudit entanglement purification and swapping procedures, we calculate the long-distance entangled-pair distribution rates and the final entangled-state fidelities for total communication distances of up to 1280 km. With three rounds of purification, entangled qudit pairs of near-unit fidelity can be distributed over 1280 km at rates of the order of, in principle, 100 Hz.


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[*] posted on 3-2-2022 at 08:24


Superconductivity in an extreme strange metal

D. H. Nguyen, A. Sidorenko, M. Taupin, G. Knebel, G. Lapertot, E. Schuberth & S. Paschen

https://doi.org/10.1038/s41467-021-24670-z

Some of the highest-transition-temperature superconductors across various materials classes exhibit linear-in-temperature ‘strange metal’ or ‘Planckian’ electrical resistivities in their normal state. It is thus believed by many that this behavior holds the key to unlock the secrets of high-temperature superconductivity. However, these materials typically display complex phase diagrams governed by various competing energy scales, making an unambiguous identification of the physics at play difficult. Here we use electrical resistivity measurements into the micro-Kelvin regime to discover superconductivity condensing out of an extreme strange metal state—with linear resistivity over 3.5 orders of magnitude in temperature. We propose that the Cooper pairing is mediated by the modes associated with a recently evidenced dynamical charge localization–delocalization transition, a mechanism that may well be pertinent also in other strange metal superconductors.


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[*] posted on 4-2-2022 at 07:09


Multicomponent superconducting order parameter in UTe 2

I. M. Hayes, D. S. Wei, T. Metz, J. Zhang, Y. S. Eo, S. Ran, S. R. Saha , J. Collini, N. P. Butch, D. F. Agterberg, A. Kapitulnik & J. Paglione

Cite as: I. M. Hayes et al., Science
DOI: 10.1126/science.abb0272 (2021).

An unconventional superconducting state was recently discovered in UTe 2 , where spin-triplet superconductivity emerges from the paramagnetic normal state of a heavy fermion material. The coexistence of magnetic fluctuations and superconductivity, together with the crystal structure of this material, suggest that a unique set of symmetries, magnetic properties, and topology underlie the superconducting state. Here, we report observations of a non-zero polar Kerr effect and of two transitions in the specific heat upon entering the superconducting state, which together suggest that the superconductivity in UTe 2 is characterized by a two-component order parameter that breaks time reversal symmetry. These data place constraints on the symmetries of the order parameter and inform the discussion on the presence of topological superconductivity in UTe 2 .


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[*] posted on 5-2-2022 at 09:54


Spatially inhomogeneous superconductivity in UTe 2

S. M. Thomas, C. Stevens, F. B. Santos, S. S. Fender, E. D. Bauer, F. Ronning, J. D. Thompson, A. Huxley, and P. F. S. Rosa

July 2021Science 373(6556):eabb0272
DOI:10.1126/science.abb0272

Newly-discovered superconductor UTe 2 is a strong contender for a topological spin-triplet state wherein a multi-component order parameter arises from two nearly-degenerate superconducting states. A key issue is whether both of these states intrinsically exist at ambient pressure. Through thermal expansion and calorimetry, we show that UTe 2 at ambient conditions exhibits two detectable transitions only in some samples, and the size of the thermal expansion jump at each transition varies when the measurement is performed in different regions of the sample. This result indicates that the two transitions arise from two spatially separated regions that are inhomogeneously mixed throughout the volume of the sample, each with a discrete superconducting transition temperature (T c ). Notably, samples with higher T c only show a single transition at ambient pressure. Above 0.3 GPa, however, two transitions are invariably observed in ac calorimetry. Our results not only point to a nearly vertical line in the pressure-temperature phase diagram but also provide a unified scenario for the sample dependence of UTe 2 .


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[*] posted on 6-2-2022 at 05:30


Universal Scaling Law for the Condensation Energy, U, Across a Broad Range of Superconductor Classes

J. S. Kim, G. N. Tam, and G. R. Stewart

DOI:10.1103/PhysRevB.92.224509
https://arxiv.org/abs/1512.06144

One of the goals in understanding any new class of superconductors is to search for commonalities with other known superconductors. The present work investigates the superconducting condensation energy, U, in the iron based superconductors (IBS), and compares their U with a broad range of other distinct classes of superconductor, including conventional BCS elements and compounds and the unconventional heavy Fermion, Sr 2 RuO 4 , Li 0.1 ZrNCl, (BEDT-TTF) 2 Cu(NCS) 2 and optimally doped cuprate superconductors. Surprisingly, both the magnitude and T c dependence (U @ T c3.4±0.2 ) of U are – contrary to the previously observed behavior of the specific heat discontinuity at T c , C, – quite similar in the IBS and BCS materials for T c >1.4 K. In contrast, the heavy Fermion superconductors’ U vs T c are strongly (up to a factor of 100) enhanced above the IBS/BCS while the cuprate superconductors’ U are strongly (factor of 8) reduced. However, scaling of U with the specific heat (or C) brings all the superconductors investigated onto one universal dependence upon T c . This apparent universal scaling U T c2 for all superconductor classes investigated, both weak and strong coupled and both conventional and unconventional, links together extremely disparate behaviors over almost seven orders of magnitude for U and almost three orders of magnitude for T c . Since U has not yet been explicitly calculated beyond the weak coupling limit, the present results can help direct theoretical efforts into the medium and strong coupling regimes.


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[*] posted on 7-2-2022 at 04:12


Core-Level Photoelectron Spectroscopy Study of UTe 2

Shin-ichi Fujimori, Ikuto Kawasaki, Yukiharu Takeda, Hiroshi Yamagami, Ai Nakamura, Yoshiya Homma and Dai Aoki

Journal of the Physical Society of Japan 90, 015002 (2021)
DOI: 10.7566/JPSJ.90.015002

The valence state of UTe 2 was studied by core-level photoelectron spectroscopy. The main peak position of the U 4 f core-level spectrum of UTe 2 coincides with that of UB 2 , which is an itinerant compound with a nearly 5 f 3 configuration. However, the main peak of UTe 2 is broader than that of UB 2 , and satellite structures are observed in the higher binding energy side of the main peak, which are characteristics of mixed-valence uranium compounds. These results suggest that the U 5 f state in UTe 2 is in a mixed valence state with a dominant contribution from the itinerant 5 f 3 configuration.


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[*] posted on 8-2-2022 at 13:56


Theory of spin-polarized superconductors –an analogue of superfluid 3 He A-phase

Kazushige Machida

https://arxiv.org/abs/2101.08963
Phys. Rev. B 104, 014514

It is shown theoretically that ferromagnetic superconductors, UGe 2 , URhGe, and UCoGe can be described in terms of the A-phase like triplet pairing similar to superfluid 3 He in a unified way, including peculiar reentrant, S-shape, or L-shape H c2 curves. The associated double transition inevitable between the A 1 and A 2 -phases in the H-T plane is predicted, both of which are characterized by non-unitary state with broken time reversal symmetry and the half-gap. UTe 2 , which has been discovered quite recently to be a spin-polarized superconductor, is analyzed successively in the same view point, pointing out that the expected A 1 -A 2 transition is indeed emerging experimentally. Thus the four heavy Fermion compounds all together are entitled to be topologically rich solid state materials worth further investigating together with superfluid 3 He A-phase.


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[*] posted on 9-2-2022 at 08:06


Spin-Orbit Coupling Induced Degeneracy in the Anisotropic Unconventional Superconductor UTe2

Alexander B. Shick, Warren E. Pickett

Phys. Rev. B 100, 134502 (2019)
DOI:10.1103/PhysRevB.100.134502

The orthorhombic uranium dichalcogenide UTe2 displays superconductivity below 1.7 K, with the anomalous feature of retaining 50% of normal state (ungapped) carriers, according to heat capacity data from two groups. Incoherent transport that crosses over from above 50 K toward a low temperature, Kondo lattice Fermi liquid regime indicates strong magnetic fluctuations and the need to include correlation effects in theoretical modeling. We report density functional theory plus Hubbard U (DFT+U) results for UTe2 to provide a platform for modeling its unusual behavior, focusing on ferromagnetic (FM, time reversal breaking) long range correlations along the a^ axis as established by magnetization measurements and confirmed by our calculations. States near the Fermi level are dominated by the j=52 configuration, with the jz=±12 sectors being effectively degenerate and half-filled. Unlike the small-gap insulating nonmagnetic electronic spectrum, the FM Fermi surfaces are large (strongly metallic) and display low dimensional features, reminiscent of the FM superconductor UGe2.


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[*] posted on 10-2-2022 at 06:31


Spin Susceptibility of the Topological Superconductor UPt 3 from Polarized Neutron Diffraction

Phys. Rev. B 96, 041111 (2017)
doi:10.1103/PhysRevB.96.041111

W. J. Gannon, W. P. Halperin, M. R. Eskildsen, Pengcheng Dai, U. B. Hansen, K. Lefmann & A. Stunault

Experiment and theory indicate that UPt 3 is a topological superconductor in an odd-parity state, based in part from temperature independence of the NMR Knight shift. However, quasiparticle spin-flip scattering near a surface, where the Knight shift is measured, might be responsible. We use polarized neutron scattering to measure the bulk susceptibility with H||c, finding consistency with the Knight shift but inconsistent with theory for this field orientation. We infer that neither spin susceptibility nor Knight shift are a reliable indication of odd-parity.


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[*] posted on 11-2-2022 at 10:38


Magnetic Properties under Pressure in Novel Spin-Triplet Superconductor UTe 2

Journal of the Physical Society of Japan 90, 073703 (2021)
https://doi.org/10.7566/JPSJ.90.073703 Dexin Li, Ai Nakamura, Fuminori Honda, Yoshiki

J. Sato, Yoshiya Homma, Yusei Shimizu, Jun Ishizuka, Youichi Yanase, Georg Knebel, Jacques Flouquet, and Dai Aoki We report the magnetic susceptibility and the magnetization under pressures up to 1.7 GPa above the critical pressure, P c ∼ 1.5 GPa, for H ∥ a, b, and c-axes in the novel spin triplet superconductor UTe 2 . The anisotropic magnetic susceptibility at low pressure with the easy magnetization a-axis changes to the quasi-isotropic behavior at high pressure, revealing a rapid suppression of the susceptibility for a-axis, and a gradual increase of the susceptibility for the b-axis. At 1.7 GPa above P c , magnetic anomalies are detected at T MO ∼ 3 K and T WMO ∼ 10 K. The former anomaly corresponds to long-range magnetic order, most likely antiferromagnetism, while the latter shows a broad anomaly, which is probably due to the development of short range order. The unusual decrease and increase of the susceptibility below T WMO for H ∥ a and b-axes, respectively, indicate the complex magnetic properties at low temperatures above P c . This is related to the interplay between multiple fluctuations dominated by antiferromagnetism, ferromagnetism, valence and Fermi surface instabilities.


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[*] posted on 12-2-2022 at 10:29


Feedback of superconductivity on the magnetic excitation spectrum of UTe 2

http://arxiv.org/abs/2107.13914v1
DOI:10.7566/JPSJ.90.113706

Stéphane Raymond, William Knafo, Georg Knebel, Koji Kaneko, Jean-Pascal Brison, Jacques Flouquet, Dai Aoki & Gérard Lapertot

We investigate the spin dynamics in the superconducting phase of UTe 2 by triple-axis inelastic neutron scattering on a single crystal sample. At the wave-vector k 1 =(0, 0.57, 0), where the normal state antiferromagnetic correlations are peaked, a modification of the excitationspectrum is evidenced, on crossing the superconducting transition, with a reduction of the relaxation rate together with the development of an inelastic peak at Ω ≈ 1 meV. The low dimensional nature and the the a-axis polarization of the fluctuations, that characterise the normal state, are essentially maintained below T sc . The high ratio Ω/k B T sc ≈ 7.2 contrasts with the most common behaviour in heavy fermion superconductors.

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[*] posted on 13-2-2022 at 13:05


Enabling Dataflow Optimization for Quantum Programs

David Ittah, Thomas Häner, Vadym Kliuchnikov, Torsten Hoefler

https://arxiv.org/abs/2101.11030

We propose an IR for quantum computing that directly exposes quantum and classical data dependencies for the purpose of optimization. The Quantum Intermediate Representation for Optimization (QIRO) consists of two dialects, one input dialect and one that is specifically tailored to enable quantum-classical co-optimization. While the first employs a perhaps more intuitive memory-semantics (quantum operations act as side-effects), the latter uses value-semantics (operations consume and produce states). Crucially, this encodes the dataflow directly in the IR, allowing for a host of optimizations that leverage dataflow analysis. We discuss how to map existing quantum programming languages to the input dialect and how to lower the resulting IR to the optimization dialect. We present a prototype implementation based on MLIR that includes several quantum-specific optimization passes. Our benchmarks show that significant improvements in resource requirements are possible even through static optimization. In contrast to circuit optimization at run time, this is achieved while incurring only a small constant overhead in compilation time, making this a compelling approach for quantum program optimization at application scale.


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[*] posted on 15-2-2022 at 10:59


A systematic mapping on quantum software development in the context of software engineering

Paulo Eduardo Zanni Jr & Valter Vieira de Camargo

https://arxiv.org/abs/2106.00926

Quantum Computing is a new paradigm that enables several advances which are impossible using classical technology. With the rise of quantum computers, the software is also invited to change so that it can better fit this new computation way. However, although a lot of research is being conducted in the quantum computing field, it is still scarce studies about the differences of the software and software engineering in this new context. Therefore, this article presents a systematic mapping study to present a wide review on the particularities and characteristics of software that are developed for quantum computers. A total of 24 papers were selected using digital libraries with the objective of answering three research questions elaborated in the conduct of this research.


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[*] posted on 17-2-2022 at 08:54


An attack to quantum systems through RF radiation tracking

Kadir Durak , Naser Jam

https://arxiv.org/pdf/2004.14445.pdf

A newfound security breach in the physical nature of single photon detectors that are generally used in quantum key distribution is explained, we found that the bit contents of a quantum key transmission system can be intercepted from far away by exploiting the ultrawideband electromagnetic signals radiated from hi-voltage avalanche effect of single photon detectors. It means that in fact any Geiger mode avalanche photodiode that is used inside single photon detectors systematically acts like a downconverter that converts the optical-wavelength photons to radio-wavelength photons that can be intercepted by an antenna as side channel attack. Our experiment showed that the radiated waveforms captured by the antenna can be used as a fingerprint. These finger prints were fed to a deep learning neural network as training data, and after training the neural network was able to clone the bit content of quantum transmission.


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[*] posted on 18-2-2022 at 09:18


Cryptographic Attack Possibilities over RSA Algorithm through Classical and Quantum Computation

Kapil Kumar Soni Akhtar Rasool

International Conference on Smart Systems and Inventive Technology (ICSSIT 2018) IEEE Xplore Part Number: CFP18P17-ART; ISBN:978-1-5386-5873-4

Cryptographic attack possibilities have several parameters and one of the possibilities is to attack over the cryptographic algorithm. Large integer factorization is still a challenging problem since the emergence of mathematics and computer science. Benchmark cryptographic protocol, the RSA Algorithm requires factorization of large integers.Classical computation does not have any polynomial time algorithm that can factor any arbitrary large integer. The remarkable but not efficient, classical algorithms for integer factorization are Trial Division, General Number Field Sieve and Quadratic Sieve. The influence of Shor’s algorithm assures to get the efficient solution of such factorization problem in polynomial time and challenges the security parameters of the existing cryptosystem, but algorithm implementation limits to be executed on a quantum computer.


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[*] posted on 19-2-2022 at 11:07


An Efficient Quantum Computing technique for cracking RSA using Shor’s Algorithm

Vaishali Bhatia & K.R. Ramkumar

2020 IEEE 5th International Conference on Computing Communication and Automation (ICCCA) Galgotias University, Greater Noida, UP, India. Oct 30-31, 2020
DOI: 10.1109/ICCCA49541.2020.9250806

Quantum Computing is a prominent word in this era as it allows computation to be performed in no time. The motive of using Quantum Computing (QC) is that even exponentially large number of problems can be solved using it which was earlier difficult with the classical computing. Conventional methods are based on usage of bits which consist of 0’s and 1’s while QC works with qubits. The main issue is that conventional computing has issue of storage as well as computation even when parallel computation is performed on it. Concept of quantum parallelism allows the computation to be performed in exponentially very low time as compared to conventional method. This paper will discuss about Quantum Computing Algorithms and how Shor’s algorithm is able to break RSA algorithms is discussed. Entanglement and superposition of qubits helps fast computation. The demonstration of the applicability has been evaluated based on computation time, storage capacity, accuracy, confidentiality, efficiency, integrity, and availability. Among various algorithms Shor’s technique is able to break various encryption algorithm with more supremacy as compared to conventional computing methods. In nutshell, paper will discuss about various QC algorithms and will illustrate how shor’s algorithm is able to crack RSA.


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[*] posted on 20-2-2022 at 06:43


Is Your Quantum Program Bug-Free?

Andriy Miranskyy, Lei Zhang and Javad Doliskani

https://doi.org/10.1145/3377816.3381731
https://arxiv.org/abs/2001.10870

Quantum computers are becoming more mainstream. As more programmers are starting to look at writing quantum programs, they face an inevitable task of debugging their code. How should the programs for quantum computers be debugged? In this paper, we discuss existing debugging tactics, used in developing programs for classic computers, and show which ones can be readily adopted. We also highlight quantum-computer-specific debugging issues and list novel techniques that are needed to address these issues. The practitioners can readily apply some of these tactics to their process of writing quantum programs, while researchers can learn about opportunities for future work.


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[*] posted on 21-2-2022 at 08:24


Are Heavy Fermion Strange Metals Planckian?

Mathieu Taupin and Silke Paschen

https://doi.org/10.3390/cryst12020251
Crystals 12, no. 2: 251.

Strange metal behavior refers to a linear temperature dependence of the electrical resistivity at temperatures below the Mott-Ioffe-Regel limit. It is seen in numerous strongly correlated electron systems, from the heavy fermion compounds, via transition metal oxides and iron pnictides, to magic angle twisted bi-layer graphene, frequently in connection with unconventional or “high temperature” superconductivity. To achieve a unified understanding of these phenomena across the different materials classes is a central open problem in condensed matter physics. Tests whether the linear-in-temperature law might be dictated by Planckian dissipation—scattering with the rate ∼ k B T/h̄, are receiving considerable attention. Here we assess the situation for strange metal heavy fermion compounds. They allow to probe the regime of extreme correlation strength, with effective mass or Fermi velocity renormalizations in excess of three orders of magnitude. Adopting the same procedure as done in previous studies, i.e., assuming a simple Drude conductivity with the above scattering rate, we find that for these strongly renormalized quasiparticles, scattering is much weaker than Planckian, implying that the linear temperature dependence should be due to other effects. We discuss implications of this finding and point to directions for further work.


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[*] posted on 22-2-2022 at 10:33


Connecting heterogeneous quantum networks by hybrid entanglement swapping

Giovanni Guccione, Tom Darras, Hanna Le Jeannic, Varun B. Verma, Sae Woo Nam, Adrien Cavaillès and Julien Laurat

https://doi.org/10.1126/sciadv.aba4508
https://arxiv.org/abs/2003.11041v2

Recent advances in quantum technologies are rapidly stimulating the building of quantum networks. With the parallel development of multiple physical platforms and different types of encodings, a challenge for present and future networks is to uphold a heterogeneous structure for full functionality and therefore support modular systems that are not necessarily compatible with one another. Central to this endeavor is the capability to distribute and interconnect optical entangled states relying on different discrete and continuous quantum variables. Here, we report an entanglement swapping protocol connecting such entangled states. We generate single-photon entanglement and hybrid entanglement between particle- and wave-like optical qubits and then demonstrate the heralded creation of hybrid entanglement at a distance by using a specific Bell-state measurement. This ability opens up the prospect of connecting heterogeneous nodes of a network, with the promise of increased integration and novel functionalities.


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[*] posted on 23-2-2022 at 08:49


Remote preparation of continuous-variable qubits using loss-tolerant hybrid entanglement of light

H. Le Jeannic, A. Cavaillès, J. Raskop, K. Huang, and J. Laurat

https://doi.org/10.1364/OPTICA.5.001012
https://arxiv.org/abs/1809.10700

Transferring quantum information between distant nodes of a network is a key capability. This transfer can be realized via remote state preparation where two parties share entanglement and the sender has full knowledge of the state to be communicated. Here we demonstrate such a process between heterogeneous nodes functioning with different information encodings, i.e., particle-like discrete-variable optical qubits and wave-like continuous-variable ones. Using hybrid entanglement of light as a shared resource, we prepare arbitrary coherent-state superpositions controlled by measurements on the distant discrete-encoded node. The remotely prepared states are fully characterized by quantum state tomography and negative Wigner functions are obtained. This work demonstrates a novel capability to bridge discrete- and continuous-variable platforms.


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