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NEAR-FUTURE APPLICATIONS of QUANTUM INFORMATION PROCESSING

NEAR-FUTURE APPLICATIONS of QUANTUM INFORMATION PROCESSING. Dr. Tal Mor Department of Computer Science Technion- Israel Institute of Technology. Quantum Information Processing is very promising. Do we need to wait 20-30 years for an application?.

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NEAR-FUTURE APPLICATIONS of QUANTUM INFORMATION PROCESSING

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  1. NEAR-FUTURE APPLICATIONS of QUANTUM INFORMATION PROCESSING Dr. Tal Mor Department of Computer Science Technion- Israel Institute of Technology

  2. Quantum Information Processing is very promising

  3. Do we need to wait 20-30 years for an application?

  4. Do we really need to wait 20-30 years for an application? Quantum Cryptography Unconditionally secure quantum key distribution (QKD) Many experimental groups implementing QKD, and obtaining a “secure” key… But is the key trulysecure also in practice? Quantum Computation Algorithmic Cooling of Spins Short-term application: improved NMR spectroscopy [Long-term result: scalable NMR Quantum Computers]

  5. Quantum Key Distribution • Non-orthogonal quantum states • No-cloning of such quantum states • Information versus disturbance (Peres-Fuchs) →Unconditionally secure “practical” quantum key distribution (in theory) Biham, Boyer, Boykin, Mor and Roychowdhury (STOC’00) Mayers (J.ACM) ; Shor and Preskill (PRL)

  6. Practical QKD But is the key truly secure also in practice??? Worldwide interest:various groups running practical QKD, performing amazing experiments Experimental Groups:J. Franson; N. Gisin; R. Hughes; P. Kwiat; E.Polzik; J. Rarity; A. Sergienko; A. Zeilinger… Companies:MAGIQ; BBN technologies; IBM; MITRE; NEC; MITSUBISHI; Idquantique; Qinetiq… Our (Technion) QKD team:Prof. Eli Biham, Prof. Meir Orenstein, Dr. Matty Katz, Mr. Oleg Izmerly

  7. Attacking QKD protocols (1) Photons are sent from Alice to Bob; The final secret key is created from the transmitted key (the raw data) via error correction and privacy amplification; • Collective attacks: Eve attaches a quantum probe to each transmitted photon (say, another photon, via a coupler), and measures these ancillary photons together, after learning all classical data, to learn optimal information on the final secret key.

  8. Attacking QKD protocols (2) The transmitted data sometimes contains two photons per pulse; • Photon Number Splitting (PNS) attacks: In PNS attacks, Eve keeps a photon from these two-photon pulses, and blocks most (or even all) single-photon pulses; If channel loss-rate is high, the legitimate users will not even notice… and Eve will get a lot (or even full) information.

  9. Worldwide Status of Security Analysis of Practical QKD None of the practical protocols is proven secure. In particular, in November 2003: • No practical scheme proven secure against Collective Attacks! • No practical scheme proven secure against Photon Number Splitting Attacks! Are these attacks realistic in the near future?

  10. Computer Science viewpoint Novel entropy manipulations techniques Algorithmic Cooling of Spins Physics viewpoint A novel cooling mechanism Nuclear Magnetic Resonance Enhanced Spin Polarization  Rapidly Increased Signal-to-Noise Ratio  Many potential applications

  11. Potential Future Applications Enhanced Polarization  Improved Signal-to-Noise ratio Applications: • Medical applications • Monitoring brain activity (for instance, a lie detector) • Identifying explosive materials • Identifying narcotics • Checking stability of materials exposed to severe conditions

  12. Nuclear Magnetic Resonance Nuclei’s spins in a magnetic field Spin-half nucleus: a quantum bit

  13. C S 1 A Simple Logic Gate A molecule with two spins  2-bit computer Manipulations of spins  a gate operating on bits Implementation of a gate: via a set of NMR pulses on a regular NMR machine

  14. Magnetic Resonance: Polarization-Bias and Temperature

  15. Polarization Enhancement (Cooling) • Data compression: some spins can be cooled quite a lot (L. Schulman & U. Vazirani) using simple logical gates, while the rest of the spins get hotter • The cold spins are pushed spatially to the edge of the molecule • Limited by Shannon’s bound on data compression • Therefore impractical

  16. Algorithmic Cooling 1. Data compression steps: 2. In addition to the computer bits, there are reset bits, namely spins that rapidly interact with the environment 3. Hot computer spins are “thermalized” via a SWAP with the reset spins (that can be re-used soon after) 4. The hot computer bits become colder. 5. The entire system is cooled Environment • This way Shannon’s bound is bypassed!

  17. Thermalization Environment Reset bits SWAP Wait “Algorithmic Cooling and Scalable NMR Quantum Computers” P. O. Boykin, T. Mor, V. Roychowdhury, F. Vatan, R. Vrijen (Proceedings of the National Academy of Science, 2002); Algorithmic Cooling is patent pending

  18. Cooling by Thermalization We succeeded tocool down2 Carbons to a low temperature of ~ 150 K TCE molecule After H Before 13 13 C C G. Brassard, J. Fernandez, R. Laflamme, T. Mor, & Y. Weinstein (on preparation) Future goals: a full algorithmic cooling (with J. Fernandez)! Much lower temperatures!! Conceptual bounds on cooling (with L. Schulman)!!! Our (Technion) research team: Prof. H. Gilboa, Dr. Matty Katz, Dr. Yael Balazs, Mr. Yossi Weinstein 1 1

  19. Summary 1. Practical QKD is not yet proven secure 2.Algorithmic Cooling is the first short-term application of quantum computing devices 1 1

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