9:00 - 9:15

Introductory Remarks by the workshop organizers

9:20 - 10:20

Mike Thewalt (SFU Burnaby, Canada): What's so special about highly enriched 28Si?

Abstract: Since the first proposals to use the electron and/or nuclear spins of shallow donor impurities in semiconductors as qubits, 28Si has held a central role. It promises to combine the highly developed Si device technology with a spin-free environment, by removing the nuclear spins of the ~5% of 29Si found in natural Si. However, highly enriched 28Si has another unique property which has nothing to do with nuclear spin, but rather arises simply from the mass differences between the stable isotopes, 28Si, 29Si and 30Si. We discovered that highly pure and dislocation free natural Si is so perfect that the linewidths of a wide variety of optical transitions are limited by inhomogeneous broadening due to this mixture of stable isotopes, via a small dependence of the band gap energy on the average isotopic mass. 28Si provides a 'semiconductor vacuum' state in which inhomogeneous broadening is almost eliminated, allowing for optical ensemble measurements which can resolve the hyperfine splitting in the neutral donor states resulting from the coupling of the donor electron spin with the donor nuclear spin. This allows us to use optical methods to both hyperpolarize the donor electron and nuclear spins, and to read out the populations in the spin states after manipulation using NMR. This has enabled us to measure coherence times for the nuclear spin of the neutral P donor in 28Si of over 180 s at cryogenic temperatures, which was a record for a solid state system. More recently we have used these same methods to study the nuclear spin of the ionized P donor, observing coherence times of 180 minutes at cryogenic temperature and 39 minutes at room temperature, far exceeding the storage times possible with any other solid state system. We will also show how these unique properties of 28Si can be used to study other interesting donor systems using optical methods.

10:20 - 10:50

Coffee break

10:50 - 11:50

Mohammad Amin (Dwave Inc., Burnaby, Canada): Decoherence induced deformation of the ground state in AQC

Abstract: Despite more than a decade of research on adiabatic quantum computation (AQC), its decoherence properties are still poorly understood. Many theoretical works have suggested that AQC is more robust against decoherence, but a quantitative relation between its performance and the qubits' coherence properties, such as decoherence time, is still lacking. While the thermal excitations are known to be important sources of errors, they are predominantly dependent on temperature but rather insensitive to the qubits' coherence. Less understood is the role of virtual excitations, which can also reduce the ground state probability even at zero temperature. In this presentation, I introduce normalized ground state fidelity as a measure of the decoherence-induced deformation of the ground state due to virtual transitions. I then show parturbative calculations of the fidelity for a single qubit and a ferromagnetic chain of qubits, emphasizing on the relation between qubits' coherence quality and the magnitude of the normalized fidelity. I finally comment on the scaling of the normalized fidelity based on realistic parameters.

[1] Q. Deng, D.V. Averin, M.H. Amin, and P. Smith, Sci. Rep. 3, 1479 (2013).

12:00 - 12:30

15:00 - 16:00

Yu-Ao Chen (USTC Shanghai, China): Linear optical quantum computation with multi-photon entanglement

Abstract: Multi-photon entanglement is central to quantum information processing, quantum simulation and precision measurement. Tremendous experimental effort has been devoted to generating multi-photon entanglement with a growing number of qubits. In this talk, I will start with a brief review of the past experimental research on linear optical quantum computation and introducing of the start-of-the-art technology in multi-photon entanglement - generation of eight photon entanglement. Then I will talk about the demonstration of topological error correction - a method that combines topological quantum computation with quantum error correction which has the highest known tolerable error rate for a local architecture. I will also show you the viability of topological error correction for fault-tolerant quantum information processing. At the end of this talk, I will show you our recent experiment progress on testing entanglement dynamics under decoherence.

16:00 - 16:30

17:00 - 19:00

9:00 - 10:00

Andrea Morello (Sydney, Australia): Single-atom spin qubits in silicon

Abstract: A phosphorus donor in silicon is, almost literally, the equivalent of a hydrogen atom in vacuum. It possesses electron and nuclear spins 1/2 which act as natural qubits [1], and the host material can be isotopically purified to be almost perfectly free of other spin species, ensuring extraordinary coherence times (~180 s) [2]. I will present the current state-of-the-art in silicon quantum information technologies, a progress that started with the single-shot readout of the spin state of an electron bound to a single P atom [3]. This method was subsequently integrated with a broadband, on-chip microwave transmission line [4] to deliver coherent electromagnetic pulses and perform arbitrary rotations of the electron spin, thereby demonstrating the first single-atom spin qubit in silicon [5]. The 31P nuclear spin can also be read out electrically - in single-shot and with fidelity > 99.8% - from a measurement of electron spin resonance, and coherently manipulated with radiofrequency pulses [6]. This yields a nuclear spin qubit in solid state with operation and readout fidelities comparable with those of ion trap systems. Finally, I will discuss current efforts to couple multiple donor qubits through the exchange interaction and perform entangling quantum logic gates. The ability to control the state of the 31P nuclear spin greatly simplifies the implementation of CNOT and SWAP gates, and allows for high-fidelity two-qubit operations without the requirement of atomic-precision in the donor locations.

[1] B. Kane, Nature 393, 133 (1998)
[2] M. Steger et al., Science 336, 1280 (2012)
[3] A. Morello et al., Nature 467, 687 (2010)
[4] J. Dehollain et al., Nanotechnology 24, 015202 (2013)
[5] J. Pla et al., Nature 489, 541 (2012)
[6] J. Pla et al., Nature (2013) in press; arXiv:1302.0047

10:00 - 10:30

15:00 - 16:00

Jay Gambetta (IBM Watson Research Center, NY, USA): Progress in superconducting qubits

Abstract: I will review IBM's current approach towards building a many-qubit architecture based on superconducting qubits. The goal is to build a system using quantum error correction schemes based on two-dimensional surface codes, which are predicted to have a remarkably high fault tolerant threshold. On the experimental side, recent advances towards implementing such surface code including the status of a three-qubit segment of the surface code are shown. Key towards long term success includes high two-qubit gate fidelities which necessitate long coherence and a high degree of qubit control. Recent progress in improving qubit coherence times is reviewed, as well as many of the potential methods to generate high fidelity two-qubit gates using only microwave control techniques.

16:00 - 17:00

Mark Johnson (Dwave, Burnaby, Canada): Overview of a Quantum Annealing Processor

Abstract: Quantum Annealing (QA), for example using a transverse field to help find the ground state of a programmable Ising Spin System, has been proposed as one of a potentially powerful set of methods to solve computationally hard problems [1,2]. D-Wave Systems Inc. has developed a processor based on this algorithm. I will introduce such a QA algorithm and discuss how superconducting flux qubits are used to implement programmable, interacting Ising spins in this processor [3]. I will then present eigenspectra of subsections of this processor measured in situ during the QA algorithm [4] and discuss implications these results have on coherence and entanglement within this system.

[1] E. Farhi et al., SCIENCE 292, pp. 472-476 (2001).
[2] T. Kadowaki and H. Nishimori, Phys. Rev. E 58 (5), pp. 5355-5363, (1998)
[3] R. Harris et al., Phys. Rev. B 82, 024511 (2010).
[4] A. J. Berkley et al., Phys. Rev. B 87, 020502(R) (2013).

Starting 17:00

Bus transfer to Stanley Park. Walk around Stanley Park (<5km= 3mi). Dinner starts at 7PM in the Teahouse in Stanley Park. Those who want to skip the walk, may get to the restaurant directly by taxi.

9:00 - 10:00

Joerg Wrachtrup (Suttgart University, Germany): The quantum way of sensing

Abstract: The precision of measurements is ultimately limited by quantum mechanics. However, achieving the quantum limit in practical measurement application like sensing proves to be a significant challenge. For certain types of spin-based sensors this is not the case. Although relying on inherently low interaction energies spins can be efficiently decoupled from their environment and are used as highly specific probes for their close environment. The talk shall describe nanoscale sensing of electric, magnetic fields, temperature etc. utilizing spin quantum sensors.

10:00 - 10:30

14:00 - 18:30

Dwave is a Canadian company dedicated to building adiabatic quantum computers. It is located in Burnaby, on the other end of Vancouver. A tour or school bus will be provided for the commute. The lab tour will be 2 - 2 1/2 hrs.

9:00 - 10:00

Alexandre Blais (Sherbrooke, Canada): Waveguide QED with an ensemble of qubits

Abstract: We study the collective effects that emerge in waveguide QED where several (artificial) atoms are coupled to a one-dimensional (1D) superconducting transmission line. Since single microwave photons can travel without loss for a long distance along the line, real and virtual photons emitted by one atom can be reabsorbed or scattered by a second atom. Depending on the distance between the atoms, this collective effect can lead to super- and subradiance, or to a coherent exchange-type interaction between the atoms. Changing the artificial atom transition frequencies is equivalent to changing the atom-atom separation and thereby opens the possibility to study the different characteristics of these collective effects. Comparison of these theoretical results to experiments performed by the ETH Zurich group will be presented.

10:00 - 10:30