Canada

We examine the thermodynamics of a new class of asymptotically AdS black holes with non-constant curvature event horizons in Gauss-Bonnet Lovelock gravity, with the cosmological constant acting as thermodynamic pressure. We find that non-trivial curvature on the horizon can significantly affect their thermodynamic behaviour. We observe novel triple points in 6 dimensions between large and small uncharged black holes and thermal AdS. For charged black holes we find a continuous set of triple points whose range depends on the parameters in the horizon geometry. We also find new generalizations of massless and negative mass solutions previously observed in Einstein gravity.

CAP Virtual Congress 2021

Thermodynamics of Exotic Gauss-Bonnet Black Holes

alternate gravity theories

black hole thermodynamics

gravitation

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technical paper

Trapped ions are a leading platform for noisy intermediate-scale quantum (NISQ) computing with high gate fidelities, long coherence times, and natural long range ion-ion interactions. QuantumION is a project which aims to scale trapped ion quantum computing to 16 Ba+ qubits while providing an open-access resource to the whole research community. High fidelity control over each ion is crucial to scalability and direct access to the hardware level is needed to make a useful community resource. This talk presents the synthesis of these two concepts exemplified by the individual addressing scheme at the heart of QuantumION. A femtosecond laser direct write (FLDW) waveguide is used to split a single laser source into 16 path-length matched and fibre coupled beams. Intensity, phase, and frequency can be controlled independently with commercial fibre AOMs. The fibre tip of each beam is imaged onto a chain of ions aided by a micro-machined array of lenses to provide individual control over 16 ions with projected $10^{-4}$ overall crosstalk. This scheme could also allow operation at multiple wavelengths opening the door to individual state readout of the ion chain with the same beam path.


*We acknowledge support from TQT (CFREF) and the University of Waterloo.

An individual optical addressing scheme for trapped Ba+ ions in an open-access quantum information processor

Understanding and controlling the properties of 2D materials to our advantage can be contemplated with the development of experimental tools to probe and manipulate electrons and their interactions at the atomic scale. In this talk, I will present scanning tunnelling microscopy and spectroscopy experiments aimed at: elucidating the nature of atomic-scale defects in 2D materials [1], visualizing moiré patterns between crystals with different symmetries [2] and imaging surface and edge states in a magnetic topological system. Moreover, I will discuss how we leverage our expertise in probing and engineering electronic states at surfaces of 2D materials to further the development of graphene-based gas sensors [3] and gated quantum dot circuits based on 2D semiconductors [4]. 

REFERENCES

[1] Plumadore et al., PRB, (2020) 
[2] Plumadore et al., Journal of Applied Physics, (2020)
[3] Rautela et al., ACS Applied Materials & Interfaces (2020) 
[4] Boddison-Chouinard, Appl. Phys. Lett., (2019)

Quantum materials at the atomic scale

In this talk I will discuss how one may view four-dimensional de Sitter space as a coherent Glauber-Sudarshan state in string theory. I will also discuss why a de Sitter space cannot exist as a vacuum state in string theory.

de Sitter space in string landscape

Bell nonlocality describes a manifestation of quantum mechanics that cannot be explained by any local hidden variable model. Its origin lies in the nature of quantum entanglement, although understanding the precise relationship between nonlocality and entanglement has been a notorious open problem. In this talk, I will describe a resolution to this problem by developing a dynamical framework in which quantum Bell nonlocality emerges as special form of entanglement, and both are unified as resources under local operations and classical communication (LOCC). The framework is built on the notion of quantum processes, which are abstract quantum channels mapping elements between fixed intervals in space and time. Entanglement is then identified as a quantum process that cannot be generated by LOCC while Bell nonlocality is the subset of these processes that have an instantaneous input- output delay time. LOCC pre-processing is a natural set of free operations in this theory, thereby enabling all entangled states to activate some form of Bell nonlocality.

Entanglement and Bell nonlocality are one and the same

I will present my group’s recent efforts to combine atomic ensembles with nanophotonic structures. I will describe our experiment in which photons emitted by a quantum dot embedded in a semiconductor nanowire are sent into an ensemble of laser-cooled caesium atoms confined inside a hollow-core photonic-crystal fibre to realize photon storage and single-photon wavelength conversion. Additionally, I will report on our progress in developing new types of mesoscopic optical cavities based on dichroic mirrors realized with chiral photonic crystal slabs and metasurfaces. This research was undertaken in part due to funding from the Canada First Research Excellence Fund.”

Nanophotonic platforms for quantum optics with atomic ensembles

To utilize the advantages of different quantum platforms, we need an interface (transducer) to transfer quantum information from one to another. Unfortunately, realistic transducers are imperfect due to, e.g. weak interaction strength or unwanted coupling. In this talk, I will present a surprising strategy to remedy the transduction imperfections: by applying a bad transducer twice [1]. I will first introduce a novel characterization of all coherent transducers by their analogous position and momentum noises. I will then show how destructive interference and measurement can be employed to eliminate the unwanted noise. I will also illustrate how the remaining noise can be corrected by using bosonic codes. Our proposal can relax the stringent technological requirement of implementing perfect transducer, and potentially enhance the speed of information transfer.

[1] Hoi-Kwan Lau and Aashish A. Clerk, npj Quantum Information 5, 31 (2019)

Realizing a perfect quantum transduction by applying a bad transducer twice

Here I discuss the possibilities to use nanomechanical resonators to converter information between microwave and optical domains. Additionally, I demonstrate an on-chip magnetic-free circulator based on reservoir-engineered electromechanical interactions. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electromechanical signal conversion paths. Finally, I show that a parametrically driven mechanical oscillator can entangle electromagnetic fields. We observe stationary emission of path-entangled microwave radiation from a micro-machined silicon nanostring oscillator, squeezing the joint field operators of two thermal modes by 3.40 (37) ~ dB below the vacuum level.

Quantum electromechanics: photon conversion, nonreciprocity, and entanglement

H2 continues to provide fundamental insights into the mechanisms of intense light-matter interactions [1]. Recently, there has been significant interest in so-called light-induced conical intersections (LICI) that arise from the angle dependence of the single-photon coupling of electronic states. Analogously to regular conical intersections, electronic and nuclear motions are strongly coupled in the vicinity of LICIs. As a signature of such rovibronic dynamics, weak modulations in the angular distribution of protons emitted from H2+ have been reported [2]. More generally speaking, infrared (IR) laser pulses couple the 1sg and 2pu electronic states of H2+ typically through several pathways involving an odd number of photons [1], which can produce complex light-induced potential energy landscapes, and consequently even richer dynamics.
In this talk we will present theory and experiment to show that the full complexity of such light-induced potential energy surfaces can be uncovered using a two-step scheme [3]. In this scheme a few cycle optical pulse projects a coherent wavepacket onto the ionic state of H2 and a weak, non-ionizing, mid-infrared, and perpendicularly polarized pulse creates the light-induced potential energy landscapes upon which the H2+ wavepacket can propagate. We observe a strongly modulated angular distribution of protons which has escaped prior observation. These modulations result directly from ultrafast dynamics on the light-induced molecular potentials and can be modified by varying the amplitude, duration and phase of the mid-infrared dressing field.

[1] H. Ibrahim, C. Lefebvre, A.D. Bandrauk, A. Staudte and F. Légaré. J. Phys. B 51, 042002 (2018).
[2] A. Natan, M.R. Ware, V.S. Prabhudesai, U. Lev, B.D. Bruner, O. Heber, and P.H. Bucksbaum, Phys. Rev. Lett. 116, 143004 (2016).
[3] M. Kübel, M. Spanner, Z. Dube, A.Yu. Naumov, S. Chelkowski, A.D. Bandrauk, M.J.J. Vrakking, P.B. Corkum, D.M. Villeneuve, and A. Staudte. Nature Communications 10, 1042 (2019).

Signatures of light-induced potential energy surfaces in H2+ - beyond conical intersections

The non-adiabatic coupling of nuclear and electronic degrees of freedom underlies many fundamental processes in Nature, including solar energy conversion and photosynthesis. The formation of electronic coherences by nuclear motion is a new aspect of such dynamics and requires new measurement techniques and methods of analysis. We will discuss Ultrafast Time-Resolved Xray Absorption and Time-Resolved Photoelectron Spectroscopy, powerful methods suited to addressing this problem. In particular, we present a new approach to fully separating electronic coherences from electronic population dynamics, a long-standing problem, based on the use and analysis of Time-Resolved Photoelectron Angular Distributions.

Coherent Ultrafast Electronic Dynamics in Molecules

Superconducting radiofrequency (SRF) cavities have been used for more than 50 years to increase the energy of charged particles. In Canada there are two accelerator centres which use SRF technology, i.e TRIUMF and the Canadian Light Source (CLS). The CLS was the first light source to use an SRF cavity in a storage ring from the beginning of operations in 2004. TRIUMF began developing SRF technology in 2000 which led in 2006 to the commissioning of the ISAC-II heavy ion superconducting linac for the post-acceleration of radioactive beams. More recently, the ARIEL SRF electron accelerator was installed at TRIUMF as a second driver for radioactive isotope production. In this talk, I will first give an overview of Canada’s SRF infrastructure and the underlying concepts. Then, I will briefly present how performance has globally evolved since the early days. Nowadays, state of the art niobium cavities reach fundamental limitations in terms of accelerating gradient (energy gain per unit length) and power dissipation. Increasing performance requires specialized chemical and surface treatments which must be tailored to specific cavity types and exploring materials beyond bulk niobium. I will highlight recent research highlights from TRIUMF and UVic including results from testing new surface treatments on unique multimode coaxial resonators and material science investigations using beta detected nuclear magnetic resonance (beta-NMR) and muon spin rotation and relaxation (muSR).

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