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Quantum entanglement is the phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in such a way that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance. The topic of quantum entanglement is at the heart of the disparity between classical and quantum physics: entanglement is a primary feature of quantum mechanics not present in classical mechanics.
Quantum key distribution (QKD) is a secure communication method that implements a cryptographic protocol involving components of quantum mechanics. It enables two parties to produce a shared random secret key known only to them, which then can be used to encrypt and decrypt messages. The process of quantum key distribution is not to be confused with quantum cryptography, as it is the best-known example of a quantum-cryptographic task.
This is a timeline of quantum computing.
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Quantum networks form an important element of quantum computing and quantum communication systems. Quantum networks facilitate the transmission of information in the form of quantum bits, also called qubits, between physically separated quantum processors. A quantum processor is a small quantum computer being able to perform quantum logic gates on a certain number of qubits. Quantum networks work in a similar way to classical networks. The main difference is that quantum networking, like quantum computing, is better at solving certain problems, such as modeling quantum systems.
An optical parametric oscillator (OPO) is a parametric oscillator that oscillates at optical frequencies. It converts an input laser wave with frequency into two output waves of lower frequency by means of second-order nonlinear optical interaction. The sum of the output waves' frequencies is equal to the input wave frequency: . For historical reasons, the two output waves are called "signal" and "idler", where the output wave with higher frequency is the "signal". A special case is the degenerate OPO, when the output frequency is one-half the pump frequency, , which can result in half-harmonic generation when signal and idler have the same polarization.
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Quantum imaging is a new sub-field of quantum optics that exploits quantum correlations such as quantum entanglement of the electromagnetic field in order to image objects with a resolution or other imaging criteria that is beyond what is possible in classical optics. Examples of quantum imaging are quantum ghost imaging, quantum lithography, imaging with undetected photons, sub-shot-noise imaging, and quantum sensing. Quantum imaging may someday be useful for storing patterns of data in quantum computers and transmitting large amounts of highly secure encrypted information. Quantum mechanics has shown that light has inherent “uncertainties” in its features, manifested as moment-to-moment fluctuations in its properties. Controlling these fluctuations—which represent a sort of “noise”—can improve detection of faint objects, produce better amplified images, and allow workers to more accurately position laser beams.
Within quantum technology, a quantum sensor utilizes properties of quantum mechanics, such as quantum entanglement, quantum interference, and quantum state squeezing, which have optimized precision and beat current limits in sensor technology. The field of quantum sensing deals with the design and engineering of quantum sources and quantum measurements that are able to beat the performance of any classical strategy in a number of technological applications. This can be done with photonic systems or solid state systems.
Jeremy O'Brien is a physicist who researches in quantum optics, optical quantum metrology and quantum information science. He co-founded and serves as CEO of the quantum computing firm PsiQuantum. Formerly, he was Professorial Research Fellow in Physics and Electrical Engineering at the University of Bristol, and director of its Centre for Quantum Photonics.
Nicolas Jean Cerf is a Belgian physicist. He is professor of quantum mechanics and information theory at the Université Libre de Bruxelles and a member of the Royal Academies for Science and the Arts of Belgium. He received his Ph.D. at the Université Libre de Bruxelles in 1993, and was a researcher at the Université de Paris 11 and the California Institute of Technology. He is the director of the Center for Quantum Information and Computation at the Université Libre de Bruxelles.
In quantum mechanics, the cat state, named after Schrödinger's cat, is a quantum state composed of two diametrically opposed conditions at the same time, such as the possibilities that a cat is alive and dead at the same time.
Linear optical quantum computing or linear optics quantum computation (LOQC) is a paradigm of quantum computation, allowing universal quantum computation. LOQC uses photons as information carriers, mainly uses linear optical elements, or optical instruments to process quantum information, and uses photon detectors and quantum memories to detect and store quantum information.
Integrated quantum photonics, uses photonic integrated circuits to control photonic quantum states for applications in quantum technologies. As such, integrated quantum photonics provides a promising approach to the miniaturisation and scaling up of optical quantum circuits. The major application of integrated quantum photonics is Quantum technology:, for example quantum computing, quantum communication, quantum simulation, quantum walks and quantum metrology.
Continuous-variable (CV) quantum information is the area of quantum information science that makes use of physical observables, like the strength of an electromagnetic field, whose numerical values belong to continuous intervals. One primary application is quantum computing. In a sense, continuous-variable quantum computation is "analog", while quantum computation using qubits is "digital." In more technical terms, the former makes use of Hilbert spaces that are infinite-dimensional, while the Hilbert spaces for systems comprising collections of qubits are finite-dimensional. One motivation for studying continuous-variable quantum computation is to understand what resources are necessary to make quantum computers more powerful than classical ones.
Spin squeezing is a quantum process that decreases the variance of one of the angular momentum components in an ensemble of particles with a spin. The quantum states obtained are called spin squeezed states. Such states have been proposed for quantum metrology, to allow a better precision for estimating a rotation angle than classical interferometers. Recently, it was shown that these states cannot provide a better precision.
Warwick Bowen is an Australian quantum physicist and nanotechnologist at The University of Queensland. He leads the Quantum Optics Laboratory, is Director of the UQ Precision Sensing Initiative and is one of three Theme Leaders of the Australian Centre for Engineered Quantum Systems.
Bound entanglement is a weak form of quantum entanglement, from which no singlets can be distilled with local operations and classical communication (LOCC).
References
- ↑ "Quantum Technology Laboratory".
- ↑ "Centre for Engineered Quantum Systems". Archived from the original on 21 July 2011. Retrieved 25 October 2010.
- ↑ "Centre for Quantum Computer and Communication Technology". Archived from the original on 15 February 2011.
- ↑ "ARC Centre of Excellence for Engineered Quantum Systems". Archived from the original on 22 July 2010.
- ↑ "ARC Centre of Excellence for Quantum Computation and Communication Technology". Archived from the original on 1 March 2011.
- ↑ "ARC Centre of Excellence for Quantum Computation Technology" (PDF). Archived from the original (PDF) on 20 February 2011.
- ↑ Heckenberg, NR; McDuff, R; Smith, CP; White, AG (1992). "Generation of optical phase singularities by computer-generated holograms". Optics Letters. 17 (3): 221–223. Bibcode:1992OptL...17..221H. CiteSeerX 10.1.1.472.1077 . doi:10.1364/OL.17.000221. PMID 19784282.
- ↑ White, AG; James, DFVJ; Eberhard, PH; Kwiat, PG (1999). "Non-maximally entangled states: production, characterisation and utilisation". Physical Review Letters. 83 (16): 3103–3106. arXiv: quant-ph/9908081 . Bibcode:1999PhRvL..83.3103W. doi:10.1103/PhysRevLett.83.3103. S2CID 18413991.
- ↑ James, DFV; Kwiat, PG; Munro, WJ; White, AG (2001). "Measurement of qubits". Physical Review A. 64 (5): 052312. arXiv: quant-ph/0103121 . Bibcode:2001PhRvA..64e2312J. doi:10.1103/PhysRevA.64.052312. S2CID 16635722.
- ↑ O'Brien, JL; Pryde, GJ; White, AG; Ralph, TC; Branning, D (2003). "Demonstration of an all-optical quantum controlled-NOT gate". Nature. 426 (6964): 264–267. arXiv: quant-ph/0403062 . Bibcode:2003Natur.426..264O. doi:10.1038/nature02054. PMID 14628045. S2CID 9883628.
- ↑ "2021 Laureate Profile: Professor Andrew White". Australian Research Council. 23 June 2021. Retrieved 4 November 2021.
- ↑ "2010 Fellows of the American Physical Society".
- ↑ "2009 Fellows of the Optical Society of America".
