IWQSE 2013 NTU Oct 15 2013 Witnessing Quantum

IWQSE 2013, NTU Oct. 15 (2013) Witnessing Quantum Coherence Yueh-Nan Chen (陳岳男) Dep. of Physics, NCKU National Center for Theoretical Sciences (South)

Outline n Coherence and entanglement n n n Cavity QED The Leggett-Garg Inequalities Witnessing Quantum Coherence in Biological Systems

Quantum Information Teleportation Dense coding Secret sharing Key distribution coherence and entanglement Quantum Computation Algorithms

Bit : 0, 1 or +, - or boy, girl…. Any two-level system 10 time t 0 t 1 t 2

Q-bit: Any two-level and physical system (Quantum bit) Two-level atom 1 0 time t 0 t 1 t 2

Two qbits : two spins time B A Spin up Spin down interaction t 0 A B Spin up Spin down Schrodinger eq. - t A B entangled state

Entanglement *. *? ( a 1 A + a 2 ) A Impossible to factory ( b 1 B + b 2 Symbol of connecting to independent system ) B

薛丁格的貓：To be or not to be?

Cavity QED

The Nobel Prize in Physics 2012 Serge Haroche David J. Wineland The Nobel Prize in Physics 2012 was awarded jointly to Serge Haroche and David J. Wineland "for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems"

• Spontaneous emission of single two-level atom n Interaction between a two-level atom and the photon reservoir: n In the interaction picture, the state vector : , where : an atom initially in the excited state : a photon of q in the radiation field

Results : where is the decay rate represents the Lamb Shift The radiation intensity distribution : , where is the energy spacing

Two-level atom inside a cavity The interaction between the atom and single-mode cavity:

Vacuum Rabi oscillations J. M. Raimond, M. Brune, and S. Haroche, Rev. Mod. Phys. 73, 565 (2001).

Vacuum Rabi splitting

Gate-confined Double Quantum Dots

Quantum Coherence in Double Quantum Dots

K. D. Petersson, J. R. Petta, H. Lu, and A. C. Gossard, PRL 105, 246804 (2010)

Question: Are they truly quantum?

The Robotic Bugs

Quantum vs Classical Bell’s Inequality: Locality and Realism

The Bell-CHSH inequality

Predictions of QM for the singlet state

QM violates the Bell-CHSH inequality

Leggett-Garg Inequality (Bell’s inequality in time) Realism and non-invasive measurement Quantum mechanics versus macroscopic realism: Is the flux there when nobody looks? Leggett and Garg, Phys. Rev. Lett. 54, 857– 860 (1985)

Palacios-Laloy, A. et al. Nature Phys. 6, 442– 447 (2010).

Distinguishing Quantum and Classical Transport through Nanostructures Transport Charge Inequality: N. Lambert, C. Emary, Y. N. Chen, and F. Nori, Phys. Rev. Lett. 105, 176801 (2010)

Double Quantum Dot

Violation of charge inequality for DQD

Quantum Transport in Organism ?

The Quantum Dimension Of Photosynthesis

Leggett-Garg inequality ? Pigments (BChl) Reaction Center

Witnessing Quantum Coherence in FMO Complex C. M. Li*, N. Lambert*, Y. N. Chen*, G. Y. Chen and F. Nori, Scientific Reports 2, 885 (2012)

Avian Magnetoreception: a tale of two spins

http: //www. technologyreview. com/blog/arxiv/27829/

Summary 1. Coherence and Entanglement 2. Cavity QED 3. The LG Inequalities 4. Quantumness in Biological Systems

Thank you for your attention!