Quantum Optics. Manipulation of «simple» quantum systems

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1 Quantum Optics Manipulation of «simple» quantum systems Antoine Browaeys Institut d Optique, Palaiseau, France

2 Quantum optics = interaction atom + quantum field e g ~ 1960: R. Glauber (P. Nobel. 2005), Now = any two level system and / or harmonic oscillator in non-classical states 2012: S. Haroche, D.J. Wineland

3 Photons IO, LKB Jussieu, LPN, Nice H V k Trapped laser-cooled atoms Internal variables Trapped laser cooled ions g e External variables LKB, IOGS, LAC Atoms-ions in cavity Cavity field, ω Trap, Ω LKB, LPN MPQ (P.7) Marseilles

Artificial atoms Superconducting circuit 2e L R

~0.1-1GHz LPN, Grenoble LAC, Cachan LPN Also: e

4 Artificial atoms Superconducting circuit 2e L R g = current + e = current - waveguide A B g = 2e, L ; e = 2e, R Quantum dots NV center in diamond CEA Saclay, Grenoble Nano-resonator Ω ~0.1-1GHz LPN, Grenoble LAC, Cachan LPN Also: e - spin, excitons, polaritons, cold molecules (LAC, LPN)

Quantum manipulations Control the number

5 Quantum manipulations Control the number of quanta Atom: Ω ~ 100 khz T ~ µk (laser cooling) Create superpositions Laser, µw e g Circuit: Ω ~ 1GHz T ~ 100 mk (fridge) Measure the state (quantum measurement) Destructive IOGS, LKB Non-destructive LKB 1 0

6 Entanglement = non-local quantum correlations Superposition A 1000 km B Einstein, Podolsky, Rosen (1935), Bell (1964): testable Aspect et al. (1982) : test

7 Generating entanglement g g ~ 4 µm

8 Generating entanglement e e + + ~ 4 µm Laser

9 Generating entanglement e e + + d A db ~ 4 µm

10 Generating entanglement e e + + d A db ~ 4 µm 2E E or 0 A + B

11 Generating entanglement e e + + d A db ~ 4 µm 2E E or 0 A + B

12 Generating entanglement e e + + d A db ~ 4 µm 2E E 0 A + B

Generating entanglement IOGS e e 2E + + d

13 Generating entanglement IOGS e e 2E + + d A db ~ 4 µm E Entanglement 0 interaction A + B Blockade ions Quantum circuit Atoms LKB, IOGS Saclay, Grenoble Challenge: interaction between photons using non-linear effects IOGS, LKB Innsbruck, Boulder, P. 7

14 Put all that together to build a quantum machine Atom j U f Superpose & entangle Creates complicated, highly-entangled states QUANTUM ENGINEERING

15 What is the machine good for?

16 Quantum information ( ) Miniaturisation components size < 0.1 nm in 2020 quantum world new ways of coding, calculating? Quantum information uses quantum laws in order to: 1. Communicate more securely Secret message Use non-classical states of light W(x, p) < 0 Thales TRT, IOGS,Jussieu, Nice 2. Calculate more efficiently Hard problems: factoring (Shor) Searching (Grover) Time calculation Exp L L n size L

17 Quantum computer = where are we in 2012? Information encoded on a quantum bit = 2-level system Small computers already exist (~10 qubits, 100 operations) Combine 1 and 2 qubit operations Ion traps: Grover, QFFT NMR: factoring 15 (!) Explore new ways of doing the calculations: more global (th.)? adiabatic computation, topological computation, probabilistic A useful Q.C should handle > 1000 qubits!!! = CHALLENGING

18 2-level system e g Quantum simulation Spin 1/2 Entangling operation Ising interaction between two spins with Quantum calculation evolution of N interacting spins Quantum simulator of condensed matter system (Feynman 1982) Already useful for ~ atoms

19 What can you simulate? High-T c supra-conductivity Topological insulator LKB, IOGS, Conductivity in presence of disorder and interactions: Anderson localization IOGS, X, Quantum magnetism P.13, LKB, Néel order frustration

20 The quantum internet J.H. Kimble (2005) LKB Jussieu Nice, LAC Quantum memory Quantum repeater Single photon sources Flying qubit Rare earth LAC Cold atoms LKB Nice Hot vapors P.6 Ion cristal P.7 LPN, IOGS, Cachan + better detectors: high QE, number resolving Also = network at telecom wavelength (1550 nm) Nice

21 Quantum metrology and squeezing Laser intensity φ Use (quantum) phase-squeezed source: Challenge: get large squeezing, using non linear medium LKB Jussieu, IOGS Application: detection of gravitational waves Virgo (E.U.), Ligo (USA)

Quantum metrology and entanglement Frequency standard F=4 ω 0 = 9 192 631

Today, best atomic clock (ion based) Δν/ν ~ 10-17 We can do better using

22 Quantum metrology and entanglement Frequency standard F=4 ω 0 = Hz F=3 133 Cs Applications: test of relativity, navigation using GPS Today, best atomic clock (ion based) Δν/ν ~ We can do better using entanglement! Prepare N atom in P e t more sensitive measurement LKB Jussieu, SYRTE

23 The devil = the environment! Quantum superposition = very fragile!! Decoherence α g + β eiφ e Environment measures Statistical (classical) mixture g, α 2 or e, β 2 The larger, the more fragile N NΓ Environment You don t see a cat dead and alive!

24 Solutions against decoherence? Error correction: quantum feedback LKB, CEA Pb: measurement perturbes Intrinsic protection: topological th. P.7 Some states are more robust than others

25 Is quantum physics the ultimate theory? Questions that quantum optics tries to answer: 1. How do you define quantum? Criteria for entanglement? 2. How big is quantum? Limit of superposition principle? How large an entangled state (in 2010 ~ 15!) Is there (and what is the meaning of) quantum classical transition?

26 Where? Paris 6 Paris 7 CEA ENS Cachan Orsay IOGS,X LPN Marcoussis Bordeaux (IO) Toulouse Grenoble Nice Marseilles

27 Research in quantum optics Labs and teams Job opportunities Contacts Events

The Nobel Prize in Physics 2012

The Nobel Prize in Physics 2012 Serge Haroche Collège de France and École Normale Supérieure, Paris, France David J. Wineland National Institute of Standards and Technology (NIST) and University of Colorado