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MadHatter
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Claimed quantum computer breakthough
https://www.wired.com/story/chinastakesclaimquantumsupre...
Food for thought. I don't know whether to believe it or not.
From opening of NCIS New Orleans  It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !


clearly_not_atara
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Supposedly a reanalysis is being done with results expected in days to weeks. I'm pretty busy right now so I see no reason to speculate; I'll let them
hash it out.
[Edited on 04201969 by clearly_not_atara]


Fyndium
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So when are the current encryption standards at stake?


MadHatter
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Safety
https://arstechnica.com/science/2020/12/uncomputablequantu...
Just when you thought it was safe to explore anything.
From opening of NCIS New Orleans  It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !


leau
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Connecting heterogeneous quantum networks by hybrid entanglement swapping
Giovanni Guccione, Tom Darras, Hanna Le Jeannic, Varun B. Verma, Sae Woo Nam, Adrien Cavaillès & Julien Laurat
Guccione et al., Sci. Adv. 2020; 6 : eaba4508 29 May 2020
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 singlephoton entanglement and hybrid entanglement between particle and wavelike optical
qubits and then demonstrate the heralded creation of hybrid entanglement at a distance by using a specific Bellstate 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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draculic acid69
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Now.or maybe soon. I wouldn't count on anything being unbreakable these days.


leau
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Teleportation Systems Toward a Quantum Internet
Raju Valivarthi, Samantha I. Davis, Cristián Peña, Si Xie , Nikolai Lauk, Lautaro Narváez, Jason P. Allmaras, Andrew D. Beyer, Yewon Gim, Meraj
Hussein, George Iskander , Hyunseong Linus Kim, Boris Korzh, Andrew Mueller, Mandy Rominsky, Matthew Shaw, Dawn Tang , Emma E. Wollman, Christoph
Simon, Panagiotis Spentzouris, Daniel Oblak, Neil Sinclair and Maria Spiropulu
PRX QUANTUM 1, 020317 (2020) DOI: 10.1103/PRXQuantum.1.020317
Quantum teleportation is essential for many quantum information technologies, including longdistance quantum networks. Using fibercoupled devices,
including stateoftheart lownoise superconducting nanowire singlephoton detectors and offtheshelf optics, we achieve conditional quantum
teleportation of timebin qubits at the telecommunication wavelength of 1536.5 nm. We measure teleportation fidelities of ≥ 90% that are consistent
with an analytical model of our system, which includes realistic imperfections. To demonstrate the compatibility of our setup with deployed quantum
networks, we teleport qubits over 22 km of singlemode fiber while transmitting qubits over an additional 22 km of fiber. Our systems, which are
compatible with emerging solidstate quantum devices, provide a realistic foundation for a highfidelity quantum Internet with practical
devices.
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Attachment: PRXQuantum.1.020317.pdf (2.3MB) This file has been downloaded 88 times
[Edited on 6122021 by leau]


macckone
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For reference purposes you need at minimum the number of qubits in a number to factor it.
They are at 5060 qubits and RSA encryption is currently using 4096 bits for long duration keys and 2048 for normal use keys.
There is a good ways to go.
The NSA has recommended against ECC for a while now, so my guess is they have a shortcut for ECC at least with some curves.


leau
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How to profit from quantum technology without building quantum computers
Dmitry Green, Henning Soller, Yuval Oreg and Victor Galitski
www.nature.com/natrevphys
150  March 2021  volume 3
There are a number of lower risk opportunities to invest in quantum technologies, other than quantum computers, but to make the most of them both
specialist knowledge and market awareness are required.
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leau
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Experimental Fockstate bunching capability of nonideal singlephoton states
Petr Zapletal, Tom Darras, Hanna Le Jeannic, Adrien Cavaillès, Giovanni Guccione, Julien Laurat & Radim Filip
Vol. 8, No. 5 / May 2021 / Optica
Advanced quantum technologies, as well as fundamental tests of quantum physics, crucially require the interferenceof multiple single photons in
linearoptics circuits. This interference can result in the bunching of photons into higher Fock states, leading to a complex bosonic behavior. These
challenging tasks timely require to develop collective criteria to benchmark many independent initial resources. Here we determine whether n
independent imperfect single photons can ultimately bunch into the Fock state ni. We thereby introduce an experimental Fockstate bunching capability
for singlephoton sources, which uses phasespace interference for extreme bunching events as a quantifier. In contrast to autocorrelation functions,
this operational approach takes into account not only residual multiphoton components but also a vacuum admixture and the dispersion of individual
photon statistics. We apply this approach to highpurity single photons generated from an optical parametric oscillator and show that they can lead to
a Fockstate capability of at least 14. Our work demonstrates a novel collective benchmark for singlephoton sources and their use in subsequent
stringent applications.
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leau
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Validating multiphoton quantum interference with finite data
Quantum Sci. Technol. 5 (2020) 045005
https://doi.org/10.1088/20589565/aba03a
Fulvio Flamini, Mattia Walschaers, Nicolò Spagnolo, Nathan Wiebe, Andreas Buchleitner and Fabio Sciarrino
Multiparticle interference is a key resource for quantum information processing, as exemplified by Boson Sampling. Hence, given its fragile nature,
an essential desideratum is a solid and reliable framework for its validation. However, while several protocols have been introduced to this end,the
approach is still fragmented and fails to build a big picture for future developments. In this work, we propose an operational approach to validation
that encompasses and strengthens the state of the art for these protocols. To this end, we consider the Bayesian hypothesis testing and the
statistical benchmark as most favorable protocols for small and largescale applications, respectively. We numerically investigate their operation
with finite sample size, extending previous tests to larger dimensions, and against two adversarial algorithms for classical simulation: the
meanfield sampler and the metropolized independent sampler. To evidence the actual need for refined validation techniques, we show how the assessment
of numerically simulated data depends on the available sample size, as well as on the internal hyperparameters and other practically relevant
constraints. Our analyses provide general insights into the challenge of validation, and can inspire the design of algorithms with a measurable
quantum advantage.
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Attachment: Validating multiphoton quantum interference with finite data.pdf (2.5MB) This file has been downloaded 87 times


leau
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Teleportation Systems Toward a Quantum Internet
Raju Valivarthi, Samantha I. Davis, Cristián Peña, Si Xie, Nikolai Lauk, Lautaro Narváez, Jason P. Allmaras, Andrew D. Beyer, Yewon Gim, Meraj
Hussein, George Iskander, Hyunseong Linus Kim, Boris Korzh, Andrew Mueller, Mandy Rominsky, Matthew Shaw, Dawn Tang, Emma E. Wollman, Christoph Simon,
Panagiotis Spentzouris, Daniel Oblak, Neil Sinclair and Maria Spiropulu
PRX QUANTUM 1, 020317 (2020)
DOI: 10.1103/PRXQuantum.1.020317
Quantum teleportation is essential for many quantum information technologies, including longdistance quantum networks. Using fibercoupled devices,
including stateoftheart lownoise superconducting nanowire singlephoton detectors and offtheshelf optics, we achieve conditional quantum
teleportation of timebin qubits at the telecommunication wavelength of 1536.5 nm. We measure teleportation fidelities of ≥ 90% that are consistent
with an analytical model of our system, which includes realistic imperfections. To demonstrate the compatibility of our setup with deployed quantum
networks, we teleport qubits over 22 km of singlemode fiber while transmitting qubits over an additional 22 km of fiber. Our systems, which are
compatible with emerging solidstate quantum devices, provide a realistic foundation for a highfidelity quantum Internet with practical
devices.
Attachment: PRXQuantum.1.020317.pdf (2.3MB) This file has been downloaded 87 times


leau
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Efficient Quantum Teleportation of Unknown Qubit Based on DVCV Interaction Mechanism
Sergey A. Podoshvedov
Entropy 2019, 21, 150; doi:10.3390/e21020150
We propose and develop the theory of quantum teleportation of an unknown qubit based on the interaction mechanism between discretevariable (DV) and
continuousvariable (CV) states on highly transmissive beam splitter (HTBS). This DVCV interaction mechanism is based on the simultaneous
displacement of the DV state on equal in absolute value, but opposite in sign displacement amplitudes by coherent components of the hybrid in such a
way that all the information about the displacement amplitudes is lost with subsequent registration of photons in the auxiliary modes. The relative
phase of the displaced unknown qubit in the measurement number state basis can vary on opposite, depending on the parity of the basis states in the
case of the negative amplitude of displacement that is akin to action of nonlinear effect on the teleported qubit. All measurement outcomes of the
quantum teleportation are distinguishable, but the teleported state at Bob’s disposal may acquire a predetermined amplitudedistorting factor. Two
methods of getting rid of the factors are considered. The quantum teleportation is considered in various interpretations. A method for increasing the
efficiency of quantum teleportation of an unknown qubit is proposed.
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[Edited on 11122021 by leau]


leau
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Scheme for the generation of hybrid entanglement between timebin and wavelike encodings
Élie Gouzien, Floriane Brunel, Sébastien Tanzilli, and Virginia D’Auria
Phys. Rev. A 102, 012603 – Published 2 July 2020
DOI:https://doi.org/10.1103/PhysRevA.102.012603
We propose a scheme for the generation of hybrid states entangling a singlephoton timebin qubit with a coherentstate qubit encoded on phases.
Compared to other reported solutions, timebin encoding makes hybrid entanglement particularly well adapted to applications involving longdistance
propagation in optical fibers. This makes our proposal a promising resource for future out ofthelaboratory 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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leau
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Small quantum computers and large classical data sets
Aram W. Harrow
https://arxiv.org/abs/2004.00026
We introduce hybrid classicalquantum algorithms for problems involving a large classical data set X and a space of models Y such that a quantum
computer has superposition access to Y but not X. These algorithms use data reduction techniques to construct a weighted subset of X called a coreset
that yields approximately the same loss for each model. The coreset can be constructed by the classical computer alone, or via an interactive protocol
in which the outputs of the quantum computer are used to help decide which elements of X to use. By using the quantum computer to perform Grover
search or rejection sampling, this yields quantum speedups for maximum likelihood estimation, Bayesian inference and saddlepoint optimization.
Concrete applications include kmeans clustering, logistical regression, zerosum games and boosting.
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leau
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Highly photon loss tolerant quantum computing using hybrid qubits
S. Omkar, Y. S. Teo, SeungWoo Lee, and H. Jeong
doi:10.1103/PhysRevA.103.032602 arXiv:2011.04209
We investigate a scheme for topological quantum computing using optical hybrid qubits and make an extensive comparison with previous alloptical
schemes. We show that the photon loss threshold reported by Omkar et al. [Phys. Rev. Lett. 125, 060501 (2020)] can be improved further by employing
postselection and multiBellstatemeasurement based entangling operation to create a special cluster state, known as Raussendorf lattice for
topological quantum computation. In particular, the photon loss threshold is enhanced up to 5.7 × 10 −3 , which is the highest reported value given
a reasonable error model. This improvement is obtained at the price of consuming more resources by an order of magnitude, compared to the scheme in
the aforementioned reference. Neverthless, this scheme remains resourceefficient compared to other known optical schemes for faulttolerant quantum
computation.
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leau
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Quantum Spin Liquid States
Yi Zhou, Kazushi Kanoda, TaiKai Ng
Rev. Mod. Phys. 89, 025003 (2017) DOI: 10.1103/RevModPhys.89.025003
This article is an introductory review of the physics of quantum spin liquid (QSL) states. Quantum magnetism is a rapidly evolving field, and recent
developments reveal that the ground states and lowenergy physics of frustrated spin systems may develop many exotic behaviors once we leave the
regime of semiclassical approaches. The purpose of this article is to introduce these developments. The article begins by explaining how
semiclassical approaches fail once quantum mechanics become important and then describes the alternative approaches for addressing the problem. We
discuss mainly spin 1/2 systems, and we spend most of our time in this article on one particular set of plausible spin liquid states in which spins
are represented by fermions. These states are spinsinglet states and may be viewed as an extension of Fermi liquid states to Mott insulators, and
they are usually classified in the category of socalled SU (2), U (1) or Z 2 spin liquid states. We review the basic theory regarding these states
and the extensions of these states to include the effect of spinorbit coupling and to higher spin (S > 1/2) systems. Two other important
approaches with strong influences on the understanding of spin liquid states are also introduced: (i) matrix product states and projected entangled
pair states and (ii) the Kitaev honeycomb model. Experimental progress concerning spin liquid states in realistic materials, including anisotropic
triangular lattice systems (κ(ET) 2 Cu 2 (CN) 3 and EtMe 3 Sb[(Pd(dmit) 2 ] 2 ), kagome lattice systems (ZnCu 3 (OH) 6 Cl 2 ) and hyperkagome
lattice systems (Na 4 Ir 3 O 8 ), is reviewed and compared against the corresponding theories.
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leau
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Probing Topological Spin Liquids on a Programmable Quantum Simulator
G. Semeghini, H. Levine, A. Keesling, S. Ebadi, T. T. Wang, D. Bluvstein , R. Verresen, H. Pichler M. Kalinowski, R. Samajdar, A. Omran, S. Sachdev ,
A. Vishwanath , M. Greiner, V. Vuletić , M. D. Lukin
DOI: 10.1126/science.abi8794
https://arxiv.org/pdf/2104.04119
Quantum spin liquids, exotic phases of matter with topological order, have been a major focus of explorations in physical science for the past several
decades. Such phases feature longrange quantum entanglement that can potentially be exploited to realize robust quantum computation. We use a
219atom programmable quantum simulator to probe quantum spin liquid states. In our approach, arrays of atoms are placed on the links of a kagome
lattice and evolution under Rydberg blockade creates frustrated quantum states with no local order. The onset of a quantum spin liquid phase of the
paradigmatic toric code type is detected by evaluating topological string operators that provide direct signatures of topological order and quantum
correlations. Its properties are further revealed by using an atom array with nontrivial topology, representing a first step towards topological
encoding. Our observations enable the controlled experimental exploration of topological quantum matter and protected quantum information
processing.
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leau
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Supplementary Materials for Probing topological spin liquids on a programmable quantum simulator
G. Semeghini et al.
Science 374, 1242 (2021) DOI: 10.1126/science.abi8794
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leau
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Quantum Teleportation Between Discrete and Continuous Encodings of an Optical Qubit
Alexander E. Ulanov, Demid Sychev, Anastasia A. Pushkina, Ilya A. Fedorov, and A. I. Lvovsky
DOI: 10.1103/PhysRevLett.118.160501
The transfer of quantum information between physical systems of a different nature is a central matter in quantum technologies. Particularly
challenging is the transfer between discrete and continuous degrees of freedom of various harmonic oscillator systems. Here we implement a protocol
for teleporting a continuousvariable optical qubit, encoded by means of lowamplitude coherent states, onto a discretevariable, singlerail
qubit—a superposition of the vacuum and singlephoton optical states—via a hybrid entangled resource we test our protocol on a onedimensional
manifold of the input qubit space and demonstrate the mappingonto the equator of the teleported qubit’s Bloch sphere with an average fidelity of
0.83  0.04. Our work opens up the way to the wide application of quantum information processing techniques where discrete and continuousvariable
encodings are combined within the same optical circuit.
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leau
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Hybrid entanglement between optical discrete polarizations and continuous quadrature variables
Jianming Wen, Irina Novikova, Chen Qian, Chuanwei Zhang and Shengwang Du
https://arxiv.org/abs/2105.04602
By coherently combining advantages while largely avoiding limitations of two mainstream platforms, optical hybrid entanglement involving both discrete
and continuous variables has recently garnered widespread attention and emerged as a promising idea for building heterogenous quantum networks.
Different from previous results, here we propose a new scheme to remotely generate hybrid entanglement between discretepolarization and
continuousquadrature optical qubits heralded by twophoton Bell state measurement. As a novel nonclassical light resource, we further utilize it to
discuss two examples of ways – entanglement swapping and quantum teloportation – in which quantum information processing and communications could
make use of this hybrid technique.
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[Edited on 23122021 by leau]
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leau
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Quantum Ising Hamiltonian Programming in Trio, Quartet, and Sextet Qubit Systems
Minhyuk Kim, Yunheung Song, Jaewan Kim and Jaewook Ahn
PRX QUANTUM 1, 020323 (2020)
DOI: 10.1103/PRXQuantum.1.020323
Rydbergatom quantum simulators are of keen interest because of their possibilities towards highdimensional qubit architectures. Here we report
continuous tuning of quantum Ising Hamiltonians of Rydberg atoms in threedimensional arrangements. Various connected graphs of Rydberg atoms
constructed with vertices and edges respectively representing atoms and Rydbergblockaded atom pairs, and their eigenenergies are probed along with
their geometric intermediates during structural transformations.Conformation spectra of star, complete, cyclic, and diamond graphs are probed for four
interacting atoms and antiprism structures for six atoms. The energy level shifts and merges of the tested structural transformations are clearly
observed with Fouriertransform spectroscopy, in good agreement with the model fewbody quantum Ising Hamiltonian. This result demonstrates the
possibility of continuous geometry tuning and thus programming of manybody spinHamiltonian systems.
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leau
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Observing crossover between quantum speed limits
Gal Ness, Manolo R. Lam, Wolfgang Alt, Dieter Meschede, Yoav Sagi & Andrea Alberti
Sci. Adv. 7, eabj9119 (2021)
DOI: 10.1126/sciadv.abj9119
Quantum mechanics sets fundamental limits on how fast quantum states can be transformed in time. Two wellknown quantum speed limits are the
MandelstamTamm and the MargolusLevitin bounds, which relate the maximum speed of evolution to the system’s energy uncertainty and mean energy,
respectively. Here, we test concurrently both limits in a multilevel system by following the motion of a single atom in an optical trap using fast
matter wave interferometry. We find two different regimes: one where the MandelstamTamm limit constrains the evolution at all times, and a second
where a crossover to the MargolusLevitin limit occurs at longer times. We take a geometric approach to quantify the deviation from the speed limit,
measuring how much the quantum evolution deviates from the geodesic path in the Hilbert space of the multilevel system. Our results are important to
understand the ultimate performance of quantum computing devices and related advanced quantum technologies.
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leau
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Resonance from antiferromagnetic spin fluctuations for superconductivity in UTe 2
Chunruo Duan, R. E. Baumbach, Andrey Podlesnyak, Yuhang Deng, Camilla Moir, Alexander J. Breindel, M. Brian Maple, E. M. Nica, Qimiao Si and Pengcheng
Dai
DOI: 10.1038/s41586021041515
https://arxiv.org/abs/2106.14424
Superconductivity has its universal origin in the formation of bound (Cooper) pairs of electrons that can move through the lattice without resistance
below the superconducting transition temperature Tc. While electron Cooper pairs in most superconductors form antiparallel spinsinglets with total
spin S=0, they can also form parallel spintriplet Cooper pairs with S=1 and an odd parity wavefunction, analogous to the equal spin pairing state in
the superfluid 3He. Spintriplet pairing is important because it can host topological states and Majorana fermions relevant for fault tolerant quantum
computation. However, spintriplet pairing is rare and has not been unambiguously identified in any solid state systems. Since spintriplet pairing is
usually mediated by ferromagnetic (FM) spin fluctuations, uranium based heavyfermion materials near a FM instability are considered ideal candidates
for realizing spintriplet superconductivity. Indeed, UTe2, which has a Tc=1.6K, has been identified as a strong candidate for chiral spintriplet
topological superconductor near a FM instability, although the system also exhibits antiferromagnetic (AF) spin fluctuations]. Here we use inelastic
neutron scattering (INS) to show that superconductivity in UTe2 is coupled with a sharp magnetic excitation at the Brillouin zone (BZ) boundary near
AF order, analogous to the resonance seen in highTc copper oxide, ironbased, and heavyfermion superconductors. We find that the resonance in UTe2
occurs below Tc at an energy Er=7.9kBTc (kB is Boltzmann's constant) and at the expense of lowenergy spin fluctuations. Since the resonance has only
been found in spinsinglet superconductors near an AF instability, its discovery in UTe2 suggests that AF spin fluctuations can also induce
spintriplet pairing for superconductivity.
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leau
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RealTime Error Correction for Quantum Computing Philip Ball Physics 14, 184  DOI: 10.1103/Physics.14.184 Random
errors incurred during computation are one of the biggest obstacles to unleashing the full power of quantum computers. Researchers have now
demonstrated a technique that allows errors to be detected and corrected in real time as the computation proceeds. It also allows error correction to
be conducted several times on a single quantum bit (qubit) during the calculation. Both features are needed to make the basic elements—the logical
qubits—of a fully errortolerant quantum computer that can be scaled up and used for applications beyond the specialized ones that these machines
have tackled so far.
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