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UNIVERSITY OF

UNIVERSITY OF. 18. 56. MARYLAND. Quantum Information Science: A Second Quantum Revolution. Christopher Monroe. Joint Quantum Institute University of Maryland Department of Physics. www.iontrap.umd.edu. Joint Quantum Institute. Quantum science for tomorrow’s technology.

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  1. UNIVERSITY OF 18 56 MARYLAND Quantum Information Science: A Second Quantum Revolution Christopher Monroe Joint Quantum Institute University of Maryland Department of Physics www.iontrap.umd.edu

  2. Joint Quantum Institute Quantum science for tomorrow’s technology

  3. Alan Turing (1912-1954) universal computing machines Claude Shannon (1916-2001) quantify information: the bit Computer Science and Information Theory Charles Babbage (1791-1871) mechanical difference engine

  4. ENIAC (1946)

  5. The first solid-state transistor (Bardeen, Brattain & Shockley, 1947)

  6. Source: Intel

  7. “There's Plenty of Room at the Bottom” (1959) Richard Feynman “When we get to the very, very small world – say circuits of seven atoms - we have a lot of new things that would happen that represent completely new opportunities for design. Atoms on a small scale behave like nothing on a large scale, for they satisfy the laws of quantum mechanics…”

  8. Quantum Mechanics: A 20th century revolution in physics • Why doesn’t the electron collapse onto the nucleus of an atom? • Why are there thermodynamic anomalies in materials at low temperature? • Why is light emitted at discrete colors? • . . . . Erwin Schrödinger (1887-1961) Albert Einstein (1879-1955) Werner Heisenberg (1901-1976)

  9. Quantum objects are waves and can be in states of superposition. • “qubit”:[0] & [1] [0] & [1] or [0] [1] The Golden Rules of Quantum Mechanics • Rule #1 holds as long as you don’t look!

  10. Most of 20th century quantum physics concerned with rule #1: • Wave mechanics • Quantized energy • Low temperature phenomena • e.g., superfluidity, BEC • Quantum Electrodynamics (QED) • Nuclear physics • Particle physics e.g., magnetism of the electron: ge = 2.00231930439 (agrees w/ theory to 12 digits)

  11. A new science for the 21st Century? Information Theory Quantum Mechanics 20th Century Quantum Information Science 21st Century

  12. What if we store information in quantum systems? classical bit: 0 or 1 quantum bit:a[0]+b[1]

  13. …BAD NEWS… Measurement gives random result f(x) e.g.,  [101] GOOD NEWS… quantum parallel processing on 2N inputs Example: N=3 qubits  = a0[000] + a1[001] + a2[010] + a3[011] a4[100] + a5[101] + a6[110] + a7[111] f(x)

  14. Deutsch (1985) Shor (1994) Grover (1996) fast number factoring N = pq fast database search …GOOD NEWS! quantum interference depends on all inputs quantum logic gates

  15. # articles mentioning “Quantum Information” or “Quantum Computing” 2000 Quantum Computers and Computing Institute of Computer Science Russian Academy of Science ISSN 1607-9817 Nature 1500 Science Phys. Rev. Lett. Phys. Rev. 1000 500 0 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

  16. quantum NOT gate: [0]  [0] + [1] [1]  [1] - [0] [0] [0]  [0] [0] [0] [1]  [0] [1] [1] [0]  [1] [1] [1] [1]  [1] [0] quantum XOR gate: ( ) e.g., [0] + [1] [0] [0][0]+ [1][1] superposition  entanglement …GOOD NEWS! quantum interference depends on all inputs quantum logic gates

  17. John Bell (1964) Any possible “completion” to quantum mechanics will violate local realism just the same Ψ = [↑][↓]-[↓][↑]

  18. Schrödinger’s Cat (1935) • [did decay][Alive] + [didn’t decay][Dead]

  19. H H Entanglement: Quantum Coins Two coins in a quantum superposition • [H][H] & [T][T] 11

  20. T T Entanglement: Quantum Coins Two coins in a quantum superposition • [H][H] & [T][T] 11 00

  21. T T Entanglement: Quantum Coins Two coins in a quantum superposition • [H][H] & [T][T] 11 00 00

  22. H H Entanglement: Quantum Coins Two coins in a quantum superposition • [H][H] & [T][T] 11 00 00 11

  23. H H Entanglement: Quantum Coins Two coins in a quantum superposition • [H][H] & [T][T] 11 00 00 11 11

  24. H H Entanglement: Quantum Coins Two coins in a quantum superposition • [H][H] & [T][T] 11 00 00 11 11 11

  25. T T Entanglement: Quantum Coins Two coins in a quantum superposition • [H][H] & [T][T] 11 00 00 11 11 11 00 .. .. ..

  26. 2. Application: Quantum Cryptography (a secure “one-time pad”) plaintext KEY ciphertext + ciphertext KEY plaintext + Comments on quantum coins: • Doesn’t violate relativity (superluminal communication): • no information transmitted in a random bit stream!

  27. Quantum Superposition From Taking the Quantum Leap, by Fred Alan Wolf

  28. Quantum Superposition From Taking the Quantum Leap, by Fred Alan Wolf

  29. Quantum Superposition From Taking the Quantum Leap, by Fred Alan Wolf

  30. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein) From Taking the Quantum Leap, by Fred Alan Wolf

  31. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein) From Taking the Quantum Leap, by Fred Alan Wolf

  32. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein) From Taking the Quantum Leap, by Fred Alan Wolf

  33. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein) From Taking the Quantum Leap, by Fred Alan Wolf

  34. Trapped Atomic Ions seven Yb+ ions ~2 mm NIST-Boulder (D. Wineland) U. Innsbruck (R. Blatt) U. Maryland & JQI (C.M.)

  35. 1 Probability [] 0 0 5 10 15 20 25 # photons collected in 100 ms “bright” 171Yb+ qubit Electronic Excited State (t ~ 8 nsec) [] Hyperfine Ground States ~GHz []

  36. 1 Probability 0 0 5 10 15 20 25 # photons collected in 100 ms 171Yb+ qubit 99.7% detection efficiency | Electronic Excited State (t ~ 8 nsec) | [] Hyperfine Ground States ~GHz [] “dark”

  37. Electronic Excited State • • • 2 [] 1 0 Hyperfine Ground States ~GHz • • • 2 ~MHz 1 [] 0 Mapping:(a[] + b[]) [0]m  [] (a[0]m + b[1]m) Cirac and Zoller, Phys. Rev. Lett. 74, 4091 (1995)

  38. Internal states of these ions entangled Trapped Ion Quantum Computer Cirac and Zoller, Phys. Rev. Lett. 74, 4091 (1995)

  39. 1 mm

  40. Ion Trap Chips Lucent/MIT Al/Si/SiO2 NIST-Boulder Au/Quartz Sandia W/Si Maryland/LPS GaAs/AlGaAs

  41. Teleportation of a single atom from here… to here…

  42. we need more qubits..

  43. Single electron quantum dots Albert Chang (Duke Univ.)

  44. B. Kane, Nature393, 133 (1998) • LPS/U. Maryland • Los Alamos • entire country of Australia Phosphorus atoms in Silicon qubit stored in 31P nuclear spin (31P: spin) (28Si: no spin) Si lattice

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