Presentation on theme: "Putting Weirdness to Use"— Presentation transcript:
1 Putting Weirdness to Use Quantum Technology:Putting Weirdness to UseThis is an architects conception of the new Physical Sciences Complex on the campus of the University of Maryland. It will be a state-of-the art laboratory facility, with excellent control over temperature, humidity, air quality, and vibration.ChrisMonroeUniversity of MarylandDepartment of PhysicsNational Institute ofStandards and Technology
2 Quantum mechanics and computing atom-sized transistors molecular-sized 2040molecular-sized2025
3 “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…”
4 Quantum Information Science A new science for the 21st Century?QuantumMechanicsInformationTheory20th Century21st CenturyQuantum Information Science
5 Computer Science and Information Theory Charles Babbage ( )mechanical difference engineAlan Turing ( )universal computing machinesClaude Shannon ( )quantify information: the bit
7 The first solid-state transistor (Bardeen, Brattain & Shockley, 1947)
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 ( )Albert Einstein ( )Werner Heisenberg ( )
9 The Golden Rules of Quantum Mechanics Rule #1: Quantum objects are waves and canbe in states of superposition.“qubit”: |0 and |1Rule #2: Rule #1 holds as long as you don’t look!|0 and |1|1|0orprobability p p
10 f(x) f(x) GOOD NEWS… quantum parallel processing on 2N inputs Example: N=3 qubits = a0 |000 + a1|001 + a2 |010 + a3 |011a4 |100 + a5|101 + a6 |110 + a7 |111f(x)N=300 qubits: more informationthan particles in the universe!…BAD NEWS…Measurement gives random resulte.g., |101f(x)Good-bad-good. Exponential storage. X2 example of parallelism.
11 …GOOD NEWS! quantum interference depends on all inputs Shor started it all
31 fast number factoring N = pq fast database search David Deutsch (1985)Peter Shor (1994)Lov Grover (1996)fast number factoring N = pqfast database search50010001500200025003000# articles mentioning “Quantum Information”or “Quantum Computing”NatureSciencePhys. Rev. Lett.Phys. Rev.2005199519902010QuantumComputersand ComputingInstitute ofComputer ScienceRussian Academyof ScienceISSN
32 Quantum Factoring application: cryptanalysis (N ~ 10200) P. Shor, SIAM J. Comput. 26, 1474 (1997)A. Ekert and R. Jozsa, Rev. Mod. Phys. 68, 733 (1996)Look for a joint property of all 2N inputse.g.: the periodicity of a function𝑓 𝑥 =sin 2𝜋 𝑥 𝑝x x x (Mod 15)etc…p = period𝑓 𝑎 𝑥 = 𝑎 𝑥 (𝑀𝑜𝑑 𝑁)r = period (a = parameter)A quantum computer can factor numbersexponentially faster than classical computers15 = 3 5= ? ?application: cryptanalysis (N ~ 10200)
33 Error-correction Redundant encoding to protect against (rare) errors Shannon (1948)Redundant encoding to protect against (rare) errorspotential error: bit flip0/10/1better off whenever p < 1/2𝑝→3 𝑝 2 1−𝑝 + 𝑝 3unprotectedprotected1/0p(error) = p𝑝(𝑒𝑟𝑟𝑜𝑟)=3 𝑝 2 1−𝑝 + 𝑝 3000/111potential error: bit flip010/101 etc..take majority
39 “Perfect” quantum measurement of a single atom state |state |# photons collected in 200msProbability3020100.2atom fluoresces 108 photons/seclaserlaseratom remains dark3020101# photons collected in 200ms>99% detection efficiency!
40 Internal states of these ions entangled Trapped Ion Quantum ComputerInternal states of these ions entangledCirac and Zoller, Phys. Rev. Lett. 74, 4091 (1995)
42 Antiferromagnetic Néel order of N=10 spins 2600 runs, a=1.12All in state All in state AFM ground state order222 eventsSince we are able to image each ion individually using the camera, we can directly observe an increase in the number of excitations as we move to long-range afm interactions. For instance, with 10 spins, we can easily see the difference between when each of our spins is up and when each is down.If we turn on our antiferromagnetic hamiltonian, we can then image our degenerate Neel ordered ground state. If we perform 2600 simulations of our AFM hamiltonian with a range of interaction parameterized by this alpha, we findAbout 220 events for each of the ground states, or 17 percent probability of landing in the ground state. Compared to the probability of falling into these states at random, it’s clear that we’re still recovering some ground state character.1:00 – 16:00219 events441 events out of = 17%Prob of any state at random =2 x (1/210) = 0.2%
43 (see K. Brown) a (C.O.M.) b (stretch) c (Egyptian) Mode competition – example: axial modes, N = 4 ionsd (stretch-2)60modeamplitudesb+cdcb2b,a+ca+bc-ab-a2ab-ac-ab+ccooling beamaa+b2b,a+cFluorescence counts402aabdcarrieraxial modes onlyc20-15-10-551015Raman Detuning dR (MHz)
53 Quantum Information Science A new science for the 21st Century?QuantumMechanicsInformationTheory20th Century21st CenturyQuantum Information SciencePhysicsChemistryComputer ScienceElectrical EngineeringMathematicsInformation Theory
55 This is an architects conception of the new Physical Sciences Complex on the campus of the University of Maryland. It will be a state-of-the art laboratory facility, with excellent control over temperature, humidity, air quality, and vibration.
56 Quantum Information Hardware at Individual atoms and photonsion trapsatoms in optical latticescavity-QEDSemiconductorsquantum dots2D electron gasesOther condensed-mattersingle atomic impurities in glasssingle phosphorus atoms in siliconSuperconductorsCooper-pair boxes (charge qubits)rf-SQUIDS (flux qubits)
57 BUT MAYBE NOT THESE GUYS! You may have heard about D-Wave, the company that claims to have already produced a quantum computerThey are learning, the hard way, that making a quantum system big is very difficult
60 Richard Feynman (1982)We have always had a great deal of difficulty in understanding the world view that quantum mechanics represents……Okay, I still get nervous with it…It has not yet become obvious to me that there is no real problem. I cannot define the real problem, therefore I suspect there’s no real problem, but I’m not sure there’s no real problem.
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