**Date:** 23 January 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** Eric Cornell, JILA

**Title: A high-energy particle experiment on a tabletop: what you can learn at 100 meV that you can't learn at 100 TeV **
**Abstract:**
Any time anyone has ever measured, the north and south poles of an electron are seen to be identical. But there are good theoretical reasons to suspect that upon closer examination we may find a discrepancy. Observing such a discrepancy would be the equivalent recording a spark chamber track of a never before seen supersymmetric particle. We will take advantage of nature's high-electric-field laboratory -- a polar molecule -- to reach new levels of sensitivity to the electon's hypothetical electric dipole moment.

**Date:** 21 March 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** Miguel Angel Martin-Delgado, Universidad Complutense de Madrid

**Title: New Lattice Gauge Theories From Quantum Computation **
**Abstract:**
I present some views and perspectives on the notions of Fault-Tolerant Quantum Computation with topological codes Next, I present current results on how the process of external quantum error correction on topological color codes (TCCs) leads to new versions of LGTs (Lattice Gauge Theories). In particular, we find that:

i/ A complete study of error correction in TCCs yields the error threshold of p_c = 4.5(2)%.

ii/ A novel Abelian lattice gauge theory with gauge group Z_2xZ_2 and a peculiar lattice and gauge structure that departs from the standard formulations of Wegner and Wilson. We refer to it as a tricolored LGT. Its structure reflects the error history in color codes, rather than the discretization of a continuous gauge theory.

iii/ A novel approach to pinpoint first-order phase transitions in LGTs with disorder using the skewness of the average over Wilson loop operators. Finally, we show how to increase the error threshold up to 18.9(3)% when noise correlations are taken into account in depolarizing channels

**Date:** 4 April 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** Masahito Ueda, The University of Tokyo

**Title: Information thermodynamics and fluctuation theorems **
**Abstract:**
The second law of thermodynamics presupposes a clear-cut
distinction between the controllable and uncontrollable degrees of
freedom by means of macroscopic operations. The cutting-edge
technologies in quantum information and nanoscience seem to require us
to abondon such a working hypothesis in favor of the distinction between
the accessible and inaccessible degrees of freedom. In this talk, I will
talk about the fundamentals of such information thermodynamics together
with the related new results on fluctuation theorems.

**Date:** 16 May 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** José Ignacio Latorre, Universitat de Barcelona

**Title: Quantum Computation of Prime Number Functions**
**Abstract:**
We propose a quantum circuit that creates a pure state corresponding to the quantum superposition of
prime numbers. This {\em Prime} state can be built
using an oracle which is a quantum implementation of the classical Miller-Rabin primality test. The {\em Prime} state is highly entangled, and its entanglement measures encode
number theoretical functions such as the distribution of twin primes or the Chebyshev bias.
This algorithm can be further combined with the quantum Fourier transform to yield an estimate of the prime counting function, more efficiently than any classical algorithm and with an error below the bound that allows for the verification of the Riemann hypothesis. Arithmetic properties of
prime numbers are then, in principle, amenable to experimental verifications on quantum
systems.

**Date:** 18 July 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** Terry Rudolph, Imperial College

**Title: QUOINS VERSUS COINS **
**Abstract:**
Human monkeys are used to thinking about the problem of choosing from a set of objects according to some desired, biased, probability distribution. Just think about how you chose your partner(s). Even when it is easy for you to do such a sampling (eg Monte Carlo sampling is sometimes easy in condensed matter physics), it can be difficult to do a quantum sampling (Q-Sampling) of the same distribution. By Q-Sampling I mean the creation of a coherent superposition of states of such objects whose amplitudes are the (square roots of) of the specified distribution. In this talk I will discuss what we do know about this problem, why it is interesting, and will discuss how it can let us achieve tasks with quantum information that are provably impossible classically. Unlike most (if not all) other such tasks in quantum information, this one does not have to do with communication per se.

**Date:** 25 July 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** Jukka Pekola, Aalto University

**Title: Energy Fluctuations and Maxwell Demon in Nano-electronic Circuits **
**Abstract:**
In small systems, such as molecules or nanostructures, energy fluctuations play an important role, and the second law of thermodynamics, for example, applies only on the average. The distribution of entropy production and the work performed under non-equilibrium conditions are then governed by so-called fluctuation relations [1 - 3]. I apply these concepts to a single-electron box [4,5], and present an experimental demonstration of fluctuation relations in them [6,7]. Single-electron circuits provide furthermore a basic example of a Maxwell Demon, where information can be converted into energy [8]; here the information is collected by a detector with single-electron sensitivity. Finally I discuss the subtle issues of work and heat in open quantum systems. I use superconducting qubits as examples of driven systems in this context [9,10].

[1] C. Jarzynski, Nonequilibrium equality for free energy differences, Phys. Rev. Lett. 78, 2690 (1997).

[2] G. E. Crooks, Entropy production fluctuation theorem and the nonequilibrium work relation for free energy differences, Phys. Rev. E 60, 2721 (1999).

[3] U. Seifert, Entropy Production along a Stochastic Trajectory and an Integral Fluctuation Theorem, Phys. Rev. Lett. 95, 040602 (2005).

[4] D.V. Averin and J.P. Pekola, Statistics of the dissipated energy in driven single-electron transitions, EPL 96, 67004 (2011).

[5] J. P. Pekola and O.-P. Saira, Work, Free Energy and Dissipation in Voltage Driven Single-Electron Transitions, J. Low Temp. Phys. 169, 70 (2012).

[6] O.-P. Saira, Y. Yoon, T. Tanttu, M. Möttönen, D. V. Averin, and J. P. Pekola, Test of Jarzynski and Crooks fluctuation relations in an electronic system, Phys. Rev. Lett. 109, 180601 (2012).

[7] J. V. Koski et al., Distribution of entropy production in nonequilibrium single-electron tunneling, arXiv:1303.6405.

[8] D. V. Averin, M. Möttönen, and J. P. Pekola, Maxwell's demon based on a single-electron pump, Phys. Rev. B 84, 245448 (2011).

[9] J. P. Pekola, P. Solinas, A. Shnirman, and D. V. Averin, Calorimetric measurement of quantum work, arXiv:1212.5808 (2012).

[10] F. W. J. Hekking and J. P. Pekola, Quantum jump approach for work and dissipation in a two-level system, arXiv:1305.5207.

**Date:** 3 October 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** Michael Berry, University of Bristol

**Title: Superoscillations and weak measurement **
**Abstract:**
Band-limited functions can oscillate arbitrarily faster than their fastest Fourier component over arbitrarily long intervals. Where such ‘superoscillations’occur, functions are exponentially weak. In typical monochromatic optical fields, substantial fractions of the domain (one-third in two dimensions) are superoscillatory. Superoscillations have implications for signal processing, and raise the possibility of sub-wavelength resolution microscopy without evanescent waves. In quantum mechanics, superoscillations correspond to weak measurements, suggesting ‘weak values’ of observables (e.g photon momenta) far outside the range represented in the quantum state. A weak measurement of neutrino speed could lead to a superluminal result without violating causality, but the effect is too small to explain the speed claimed in a recent experminent.

**Date:** 28 November 2013, 4pm

**Venue:** CQT Seminar Room, S15-03-15

**Speaker:** Masanao Ozawa, Nagoya University

**Title: Uncertainty Principle and Quantum Reality **
**Abstract:**
Abstract: In this talk, I will review my proposal to reformulate Heisenberg's uncertainty principle [1-3] and its recent experimental confirmation [6]. The new formulation allows us simultaneous measurements of totally non-commuting observables [4].
We will discuss how this affects our understanding of quantum reality along the line with a recent mathematical reconstruction of Bohr's reply to Einstein-Podolsky-Rosen on their paradox [5].

References.

[1] M. Ozawa, Universally valid reformulation of the Heisenberg
uncertainty principle on noise and disturbance in measurement, Phys. Rev. A 67, 042105/1-042105/6 (2003).

[2] M. Ozawa, Uncertainty principle for quantum instruments and
computing, Int. J. Quant. Inf. 1, 569--588 (2003).

[3] M. Ozawa, Uncertainty relations for noise and disturbance in
generalized quantum measurements, Ann. Phys. (N.Y.) 311, 350-416 (2004).

[4] M. Ozawa, Quantum reality and measurement: A quantum logical
approach, Found. Phys. 41, 592-607 (2011).

[5] M. Ozawa and Y. Kitajima, Reconstructing Bohr's Reply to EPR in
Algebraic Quantum Theory, Found. Phys. 42, 475-487 (2012).

[6] J. Erhart, S. Sponar, G. Sulyok, G. Badurek, M. Ozawa, and Y.
Hasegawa, Experimental demonstration of a universally valid error-disturbance uncertainty relation in spin-measurements, Nature Phys. 8,
185-189 (2012).