Barbara Kraus

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Barbara Kraus (born 26 December 1975) [1] ) is an Austrian physicist specializing in quantum information, quantum entanglement, and quantum key distribution. She is a University Professor at the TUM School of Natural Sciences at the Technical University of Munich.

Contents

Education and career

Kraus is originally from Innsbruck. [2] She studied mathematics and physics at the University of Innsbruck, earning diplomas in mathematics and physics. She completed her PhD in physics under the supervision of Ignacio Cirac in 2003. After postdoctoral research at the Max Planck Institute of Quantum Optics, the University of Geneva, and the University of Innsbruck, she became an assistant professor in Innsbruck in 2010, and earned her habilitation there in 2012. [3] She became full professor in 2020. [4] In 2023 she was appointed professor of Quantum Algorithms and Applications at the Technical University of Munich. [5]

Research

Kraus is best known for her work in quantum information and especially in entanglement theory. Together with her coworkers she developed criteria to decide whether a quantum state is separable or entangled and showed how to construct optimal entanglement witnesses [6] and studied the creation of entanglement by unitary quantum gates [7] and dissipative processes. [8] In 2010 she showed how to decide whether two pure quantum states of a many-particle system are equivalent to each other in terms of entanglement. [9] More recently she introduced the notion of "maximally entangled sets" as a new concept generalizing maximally entangled states to the case of considering entanglement between more than two systems (multipartite entanglement). [10] In the field of quantum cryptography, she studied the security of key-distribution protocols and the achievable secret-key rates. Among other results, she and her collaborators Renato Renner and Nicolas Gisin gave an influential information-theoretic security proof for the security of a quantum key distribution protocol [11]

Recognition

Kraus won a Start-Preis from the Austrian Science Fund in 2010. [3] She was the 2011 winner of the Ludwig Boltzmann Prize of the Austrian Physical Society, [12] [13] and the 2013 winner of the Lieben Prize of the Austrian Academy of Sciences for her work on many-body entanglement. [2] She became a member of the Young Academy of the Austrian Academy of Sciences in 2014. [14]

Related Research Articles

<span class="mw-page-title-main">Quantum entanglement</span> Correlation between quantum systems

Quantum entanglement is the phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such 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.

A Bell test, also known as Bell inequality test or Bell experiment, is a real-world physics experiment designed to test the theory of quantum mechanics in relation to Albert Einstein's concept of local realism. Named for John Stewart Bell, the experiments test whether or not the real world satisfies local realism, which requires the presence of some additional local variables to explain the behavior of particles like photons and electrons. To date, all Bell tests have found that the hypothesis of local hidden variables is inconsistent with the way that physical systems behave.

In quantum mechanics, separable states are quantum states belonging to a composite space that can be factored into individual states belonging to separate subspaces. A state is said to be entangled if it is not separable. In general, determining if a state is separable is not straightforward and the problem is classed as NP-hard.

<span class="mw-page-title-main">Greenberger–Horne–Zeilinger state</span> "Highly entangled" quantum state of 3 or more qubits

In physics, in the area of quantum information theory, a Greenberger–Horne–Zeilinger state is a certain type of entangled quantum state that involves at least three subsystems. The four-particle version was first studied by Daniel Greenberger, Michael Horne and Anton Zeilinger in 1989, and the three-particle version was introduced by N. David Mermin in 1990. Extremely non-classical properties of the state have been observed. GHZ states for large numbers of qubits are theorized to give enhanced performance for metrology compared to other qubit superposition states.

The W state is an entangled quantum state of three qubits which in the bra-ket notation has the following shape

Time-bin encoding is a technique used in quantum information science to encode a qubit of information on a photon. Quantum information science makes use of qubits as a basic resource similar to bits in classical computing. Qubits are any two-level quantum mechanical system; there are many different physical implementations of qubits, one of which is time-bin encoding.

Quantum cloning is a process that takes an arbitrary, unknown quantum state and makes an exact copy without altering the original state in any way. Quantum cloning is forbidden by the laws of quantum mechanics as shown by the no cloning theorem, which states that there is no operation for cloning any arbitrary state perfectly. In Dirac notation, the process of quantum cloning is described by:

In quantum information and quantum computing, a cluster state is a type of highly entangled state of multiple qubits. Cluster states are generated in lattices of qubits with Ising type interactions. A cluster C is a connected subset of a d-dimensional lattice, and a cluster state is a pure state of the qubits located on C. They are different from other types of entangled states such as GHZ states or W states in that it is more difficult to eliminate quantum entanglement in the case of cluster states. Another way of thinking of cluster states is as a particular instance of graph states, where the underlying graph is a connected subset of a d-dimensional lattice. Cluster states are especially useful in the context of the one-way quantum computer. For a comprehensible introduction to the topic see.

Quantum lithography is a type of photolithography, which exploits non-classical properties of the photons, such as quantum entanglement, in order to achieve superior performance over ordinary classical lithography. Quantum lithography is closely related to the fields of quantum imaging, quantum metrology, and quantum sensing. The effect exploits the quantum mechanical state of light called the NOON state. Quantum lithography was invented at Jonathan P. Dowling's group at JPL, and has been studied by a number of groups.

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References

  1. "Curriculum Vitae" (pdf). tum.de. 2022-02-23.
  2. 1 2 Barbara Kraus receives Ignaz L. Lieben Prize, Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, 2 December 2013, retrieved 2020-01-05
  3. 1 2 Curriculum vitae (PDF), 2018, retrieved 2020-01-05
  4. "Institute for Theoretical Physics: Staff". uibk.ac.at. Retrieved 2020-02-16.
  5. "TUM Professors: Kraus Barbara". tum.de. Retrieved 2023-07-25.
  6. Lewenstein, M.; Kraus, B.; Cirac, J. I.; Horodecki, P. (2000). "Optimization of entanglement witnesses". Phys. Rev. A. 62 (5): 052310. arXiv: quant-ph/0005014 . doi:10.1103/PhysRevA.62.052310. S2CID   119458600.
  7. Kraus, B.; Cirac, J. I. (2001). "Optimal creation of entanglement using a two-qubit gate". Phys. Rev. A. 63 (6): 062309. arXiv: quant-ph/0011050 . doi:10.1103/PhysRevA.63.062309. S2CID   35720838.
  8. Kraus, B.; Büchler, H. P.; Diehl, S.; Kantian, A.; Micheli, A.; Zoller, P. (2007). "Preparation of entangled states by quantum Markov processes". Phys. Rev. A. 78 (4): 042307. arXiv: 0803.1463 . doi:10.1103/PhysRevA.78.042307. S2CID   118376008.
  9. B. Kraus (2010). "Local Unitary Equivalence of Multipartite Pure States". Phys. Rev. Lett. 104 (2): 020504. arXiv: 0909.5152 . doi:10.1103/PhysRevLett.104.020504. PMID   20366579. S2CID   29984499.
  10. de Vicente, J. I.; Spee, C.; Kraus, B. (2013). "Maximally Entangled Set of Multipartite Quantum States". Phys. Rev. Lett. 111 (11): 110502. arXiv: 1305.7398 . doi:10.1103/PhysRevLett.111.110502. PMID   24074062. S2CID   24612228.
  11. Renner, Renato; Gisin, Nicolas; Kraus, Barbara (2005). "Information-theoretic security proof for quantum-key-distribution protocols". Phys. Rev. A. 72: 012332. arXiv: quant-ph/0502064 . doi:10.1103/PhysRevA.72.012332. S2CID   119052621.
  12. "Auszeichnung für Innsbrucker Quantenphysikerin", Der Standard (in German), 15 June 2011
  13. Preis für Innsbrucker Quantentheoretikerin (in German), ORF, June 15, 2011
  14. Barbara Kraus, Austrian Academy of Sciences, retrieved 2020-01-05