1 / 24

Lecture 5 Quantum Information 1: Quantum Communication & Quantum Cryptography

Lecture 5 Quantum Information 1: Quantum Communication & Quantum Cryptography. Note: HWK2 posted on course web, due next Wed 2/12 in class. Course Outline. Part 1: basic review: Optics+Quantum; Part 2: Basic Light-matter interaction; laser; Part 3: Quantum Optics of photons

wyanet
Download Presentation

Lecture 5 Quantum Information 1: Quantum Communication & Quantum Cryptography

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 5Quantum Information 1: Quantum Communication & Quantum Cryptography Note: HWK2 posted on course web, due next Wed 2/12 in class

  2. Course Outline Part 1: basic review: Optics+Quantum; Part 2: Basic Light-matter interaction; laser; Part 3: Quantum Optics of photons Part 4: More advanced light-matter interaction Part 5: Quantum information/photonics/ applications Subject to change; Check updates on course web/wiki

  3. This Lecture • Quantum Information Science 1: quantum (secure) communication & quantum cryptography (photon based) (cf. *FQ Chap12) Learn more: M. Le Blanc: A Short Introduction to Quantum Information and Quantum Computation Chuang & Nielson, QCQI David Mermin, Quantum Computer Science: An Introduction Good to reach on beach or train: J. Dowling’s Schrodinger’s Killer App L. Susskind, Quantum Mechanics: The Theoretical Minimum (see also Stanford course lectures/videos of same title) N. Gisin et al. Rev. Mod. Phys. 74, 145–195 (2002) J.W.Pan Lecture: http://quantuminformation.physi.uni-heidelberg.de/pic/LEC430.pdf MIT 6.453 course on quantum communication http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-453-quantum-optical-communication-fall-2008/ Shapiro-Wong Group: http://www.rle.mit.edu/qoptics/

  4. See also http://www.youtube.com/ watch?v=tKfyw-uAgac From :C. Bennett lecture “Information is quantum” [highly recommended to read] http://researcher.watson.ibm.com/researcher/files/us-bennetc/QInfWeb.pdf

  5. Classical Cryptography (Secure Communication) ENIGMA RSA-100=37975227936943673922808872755445627854565536638199 × 40094690950920881030683735292761468389214899724061 Earn $200,000 to factorize RSA-2048 Later quantum computing will break this RSA RSA-100 =15226050279225333605356183781326374297180681149613 80688657908494580122963258952897654000350692006139

  6. The purpose of quantum cryptography is to provide a reliable method for transmitting a secret key and knowing that no-one has intercepted it along the way. The method is founded on the fundamental laws of quantum physics, and the process of sharing a secret key in a secure way is called quantum key distribution. • Two basic schemes for quantum cryptography, using • basic principles of quantum measurements on single particles (photons) • The properties of entangled photon properties of entangled states.

  7. Classical communication & evesdropper

  8. Photon polarization qbits

  9. Review 2-state QM (d=2 Hilbert space) R2 representation

  10. Quantum No Cloning Theorem http://courses.cs.washington.edu/courses/ cse599d/06wi/lecturenotes4.pdf

  11. QKD by BB84 Protocol (ex.12.3) http://www1.cse.wustl.edu/~jain/cse571-07/ftp/quantum/index.html Interesting read on B&B http://researcher.watson.ibm.com/researcher/view.php?person=us-bennetc http://www.noodls.com/view/C72E62DBAF2DB94324F14C95042A47D40F3E72EF (also discovered q. teleportation)

  12. Reality Complications Reduced key length Missing photons .. Reduce # of useful bits Birefringence (change polarization during transmission) Detector dark counts (false click even with missing photons) address by (classical) Error correction General Read: “Quantum cryptography: Seeking absolute security” http://www.nature.com/nature/journal/v447/n7143/full/447372a.html

  13. Hardware requirements/complications • (reliable) Single photon source [multiphoton emission compromises security by giving Eve more chances to evade detection (both Eve’s detectors click  knows basis wrong)] • Attenuated single-freq laser: photon Poisson distr, subject to multi-photons • “on-demand” single photon source [current research] (will revisit this when discussing QO) • (reliable) single photon detectors, polarization rotators, medium

  14. Transmission Media for quantum communication/cryptography Subject to environmental noise (air turb. stray light etc.) <possible project/essay> Phase (vs polarization) encoding Subject to loss and birefringence (at long distance)

  15. See also : http://qwcap.com (potential essay topic, explain how these work, or market analysis)

  16. Quantum communication in space (use entanglement) (another example potential essay topic, explain how this work) http://www.nature.com/news/data-teleportation-the-quantum-space-race-1.11958

  17. QKD based on entanglement (Eckert protocol)

  18. Entanglement based QKD Related to idea of “quantum illumination” (entanglement enhanced quantum sensing/detection) S. Lloyd, “Enhanced Sensitivity of Photodetection via Quantum Illumination,” Science 321, 1463 (2008). A modern example A secure communication channel that relies on quantum entanglement survives despite the noisy break up of the entanglement itself. Viewpoint: Don’t Cry over Broken Entanglement http://physics.aps.org/articles/v6/74 Entanglement’s Benefit Survives an Entanglement-Breaking Channel Zheshen Zhang, Maria Tengner, Tian Zhong, Franco N. C. Wong, and Jeffrey H. Shapiro Phys. Rev. Lett. 111, 010501 (2013)

  19. Next Lecture (5): Light Matter Interaction --- Radiative Transition in Atoms • FQ Chap 4

More Related