Mesoscopic Physics Introduction Prof. I.V.Krive lecture presentation Address: Svobody Sq. 4, 61022, Kharkiv, Ukraine, Rooms. 5-46, 7-36, Phone: +38(057) , Testing the Limits of Quantum Mechanics Diffraction of fullerenes in free space T~ K, excitation energy ~7 eV, 174 vibration degrees of freedom, infrared photons ~10 m, Hot, neutral C60 molecules leave the oven, pass through collimating slits, traverse a SiN grating and are detected via thermal ionization by a laser 1.25 m behind the grating Graphene, Graphite, SWNT, Fullerene Atomic Wires of Carbon The atomic chains (up to 16 carbon in a row) have been observed to survive for more than 100 s. Quantum Information Theory Feynman 1982: Simulation of deterministic process on classical computer is easy: a*N space for N particles Simulation of random process on classical computer is difficult: a N space; exponentially large time/memory required => stochastic algorithms may help Simulation of quantum systems on classical computer is similarly difficult. N spins 1/2 : Evolution is described by unitary matrix in Hilbert space of 2 N dimensions. Stochastic algorithm will not help: Bells inequality! Quantum simulator is needed Feynman, Int. J. Theor. Phys. 21, 467 (1982) Deutsch 1985: Quantum complexity can be used to efficiently solve difficult problems; quantum Turing machine Deutsch, Proc. R. Soc. Lond. A 400, 97 (1985) John Bell David Deutsch Requirements (DiVincenzo) Long decoherence time ( operation time) Set of universal gates Qubit readout Initialization possibility Scalability How to build qubit? mIcroscopic two-level systems: atomic/photonic/solid state mAcroscopic: quantum electrical circuits quantum control How is it done? Quantum Bits Nobel Prize in Physics 2012 Serge Haroche (right) and assistant Igor Dotsenko (left) at work in the laboratory. David J. Wineland in his laboratory, adjusting a n ultraviolet laser beam used to manipulate ions in a high-vacuum apparatus containing an ion trap. These devices are used to demonstrate the basic operations required for a quantum computer. Cavity QED Measuring and Manipulating Individual Quantum Systems Innsbruck teleportation machine (R. Blatt) Transmon and cavity QED co-planar wave guide resonator Josephson junctions capacitor & antenna wave guide Flux regime E J >> E C Wallraff et al., Nature 431, 162 (2004) Quantum Annealer D-Wave's "Quantum computers Photograph of a chip constructed by D-Wave Systems Inc., designed to operate as a 128-qubit superconducting adiabatic quantum optimization processor (Quantum Annealer). Simplified schematic of a superconducting flux qubit acting as a quantum mechanical spin. Circulating current in the qubit loop gives rise to a flux inside, encoding two distinct spin states that can exist in a superposition.