WIPC 2017 - Day 1

From Atomic Physics to Cosmology: The Physics Life of a Black Femme

The discovery of the Higgs boson reinforces the possibility that similar, scalar particles may exist in nature and could drive cosmological inflation. In this talk I will describe my scientific research in theoretical cosmology through the lens of my experience as a Black, Jewish, queer and femme physicist. I will describe my work with the dark matter candidate, the axion, as well as efforts to describe the universe before it was a second old, the inflationary era. I will talk about the exciting claim that dark matter axions form an exotic state of matter called a Bose-Einstein condensate and my ownwork on this idea. Along the way, I will reflect on what it means to consider these ideas while being a Black femme.

Affiliation: University of Washington

Quantum theory of time

It is a rare situation where we need to cast aside elementary assumptions that underpin our theories in order to advance them further.  To be an advance two things are required: (1) any discarded assumption must be accounted for as a consequence of something deeper, and (2) the deeper cause must have consequences (predictions) that show it is necessary. 

I suspect that advancing our understanding of the nature of time, and dynamics in particular, is a situation of this kind.  Dynamics is conventionally assumed to be an elemental part of nature. It is incorporated axiomatically in physical theories through conservation laws and compliant equations of motion. If, however, the conservation laws and equations of motion were found to be due to deeper causes, the conventional view of dynamics being elemental would need reworking. I will show how a violation of time reversal symmetry (T violation) of the kind observed in K and B meson decay might be such a cause. 

I use a new quantum formalism based on the principle of superposition of multiple paths that treats time and space equally.  The states of matter and fields are represented by paths over space and time.  If there is no T violation, the formalism allows an object to be localised in both space and time, i.e. it would exist only in some small region of space and in some small interval of time.  As the object would not exist before or after the time interval, there is no equation of motion and no conservation laws.  The elementary assumption of dynamics has been clearly discarded here.

However, the same formalism with T violation is dramatically different.  The T violation induces destructive interference between paths over time which makes it impossible for matter to remain localized at any one position.  An equation of motion (the Schrodinger equation) emerges and conservation laws are obeyed.  The discarded assumption is replaced with the emergence of dynamics as a consequence of T violation. Requirement 1 is satisfied.

Moreover, local variations in T violation induce corresponding variations in local clock time (like a quantum version of time dilation). I will briefly discuss how this might lead to physical evidence of the necessity of the new formalism and how it might fulfil requirement 2.

Affiliation: Griffith University

A more inclusive atmosphere enhances innovation and the quality of life for everyone. Diversity in science is an issue which we should all be concerned with if we want healthy programs that reverse enrollment trends. Panelists will share their experiences and offer advice on how to increase diversity, including strategies on how to make programs and careers in physics more accessible to women. 

Moderated by

Melanie Campbell, University of Waterloo

Panelists

Chanda Prescod-Weinstein, University of Washington
Chris Herdman, Institute for Quantum Computing
Serge Villemure, Natural Sciences and Engineering Research Council of Canada (NSERC)
Shohini Ghose, Wilfrid Laurier University

Quantum black hole holograms

Almost twenty years ago, J.Maldacena made a remarkable insight into the structure of both quantum field theories and quantum gravity called the AdS/CFT correspondence. Its most intriguing feature is that the (Anti de Sitter) gravity theory involved has one more spatial dimension than the (Conformal) Field Theory to which it is physically equivalent. This is reminiscent of a hologram, like the 3D picture of you on your 2D driver's licence. Furthermore, AdS physics is easy to calculate when CFT physics is not, and vice versa. This sparked applications to modelling systems as diverse as quantum critical points in condensed matter, the quark-gluon plasma, and cosmology. Other advances developed conceptual connections between the geometry of spacetime and information theoretic entanglement. Our specific focus is on using holographic CFT tools to make progress on two grand puzzles: how do classical black hole spacetimes emerge from quantum string theory, and how can information that falls into black holes be recovered? This talk will assume no prior knowledge of any of these topics.

Afiliation: University of Toronto

Melting Nuclei

Nuclei are melted in high energy collisions at the Relativistic Heavy Ion Collider (RHIC) on Long Island and the Large Hadron Collider (LHC) in Geneva, forming a liquid of quarks and gluons called the Quark Gluon Plasma (QGP).  Measurements at RHIC and the LHC cover two orders of magnitude in center of mass energy, corresponding to nearly an order of magnitude in energy density.  This phase of matter existed shortly after the Big Bang.  As it expands and cools, it refreezes, forming particles called hadrons.  We determine the properties of the QGP by studying these hadrons.

Affiliation: University of Tennessee

Many professionals with a physics degree leave academia for jobs in the private sector, pursuing a career where their co-workers have drastically different educational backgrounds relative to theirs. With an array of options available, we gathered professionals from both academia and the private sector to offer you with insight on how an education in physics can be applicable to many careers and the pros and cons of each career type.

Moderated by

Melanie Campbell, University of Waterloo

Panelists

Jon Walgate, University of Waterloo
Michael Burns, Waterloo Collegiate Institute
Michelle Irvine, Google
René Stock, Scotiabank

Weak measurements, decoherence and cosmology

In this work we consider a recent proposal in which gravitational interactions are mediated via  the exchange of classical information and apply it to a quantized Friedman-Robertson-Walker (FRW) universe with the assumption that any test particles must feel a classical metric. We show that such a model results in decoherence in the FRW state that manifests itself as a dark energy fluid that fills the spacetime. Motivated by quantum-classical interactions this model is yet another example of theories with violation of energy-momentum conservation whose signature could have significant consequences for the observable universe

Affiliation: University of Waterloo and Perimeter Institute

The Search for a Central Black Hole in the Large Magellanic Cloud

As one of our closest galactic neighbours, the center of the Large Magellanic Cloud (LMC) is an enticing place to look for a central black hole (BH). Due to the large size of the LMC on the sky and the complexity of its dynamics, the center of this dwarf galaxy is still only known to ∼ 30 arcmin. Here we present a new study of the stellar kinematics near the center of the LMC, and use this to provide the first constraints on the possible presence of a central black hole.

With the impressive field of view of the Multi Unit Spectroscopic Explorer (MUSE) for the Very Large Telescope this is the largest region of the LMC mapped with integrated light. We identify and subtract the galactic foreground population and use the Calcium Triplet (∼ 850nm) spectral lines to create a 2D radial velocity map with an unprecedented spatial resolution of 1 arcmin2.

Comparison of this map with kinematic models yields 3σ upper-mass-limit of 9 × 10^6 M⊙ for any black hole within the center of the LMC. The study of such a nearby dwarf galaxy and its potential black hole can shed light on many theories of BH formation, growth, and host system interaction.

Affiliation: McGill University

Red but not dead: a multiwavelength exploration of unexpected star formation in SpARCS Brightest Cluster Galaxies

We have conducted a comprehensive infrared photometric and optical spectroscopic campaign of the largest sample of Brightest Cluster Galaxies (BCGs), those selected from the Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS). Given the tension that exists between model predictions and recent observations of BCGs at z<2, we aim to uncover the dominant physical mechanism(s) guiding the stellar mass buildup of this special class of galaxies, the most massive in the Universe and uniquely residing at the centres of galaxy clusters.

Through an unprecedented study of the far-infrared spectral energy distributions (SEDs) of 675 SpARCS BCGS between 0 < z < 1.8, and the stacked optical spectra of 93 BCGs between 0.1 < z < 1.1, we discover unexpected star formation activity occurring within these galaxies during an epoch where they are predicted to be largely devoid of material to form stars. The star-forming model fits to the broadband (3.6-500 microns) Spitzer/Herschel, far-infrared BCG SEDs are confirmed by the direct detection of emission-line signatures of ionized gas in the optical spectra. In the optical spectra we also detect the Balmer stellar absorption features and '4000 Angstrom break' indexes characteristic of a younger stellar population than anticipated for these supposed 'red and dead' elliptical galaxies.

The discovery of vigorously star-forming BCGs down to z~0.5 challenges the accepted belief that these galaxies should only passively evolve through gas-poor, 'dry' mergers since z~4. However, it does agree with relatively recent refinements to the semi-analytic model of hierarchical structure formation that is invoked to explain BCG formation and evolution. We attribute the observed star formation to 'wet' (gas-rich) mergers and internal stellar mass losses, based on a lack of key signatures (to date) of the 'cluster cooling flows' which are usually considered to be the source of star formation in this unique class of galaxies.

Affiliation: McGill University

The dynamical friction effects of neutrinos as seen in the TianNu simulation

Standard big bang cosmology predicts a cosmic neutrino background at given temperature today. Neutrino velocities are expected to be non-relativistic today.  We had earlier made predictions for the dynamical friction of haloes, as a result of the neutrino wakes, moving in a stream of neutrinos. In this talk, I will quantify how we extract this signal from a neutrino+dark matter simulation.

Affiliation: University of Waterloo and Perimeter Institute

Spectral manipulation of entangled photons with an upconversion time lens

Sources of entangled photons with precisely controlled properties are necessary for effective and efficient photonic quantum communication, computation, and metrology. The nonlinear process of spontaneous parametric downconversion (SPDC) provides a reliable source of energy-time entangled photons, but most SPDC sources tend to produce photons with frequency anti-correlations. Photon pairs with positively correlated spectra may be useful for quantum-enhanced clock synchronization [1], but control over the correlations after state generation has not yet been demonstrated. Spectral control over a photon after it has been created is highly desirable for ultrafast manipulation and state engineering, especially at wavelengths where materials with suitable phasematching do not exist [2, 3].

A time lens operates on the temporal and frequency distributions of light in the same way that a conventional glass lens manipulates the spatial and momentum profiles of a beam [4]. Chromatic dispersion, or chirping, spreads the temporal profile of a beam such that each temporal slice of the beam has a distinct central frequency. One promising implementation of a time lens combines a single photon with a strong classical escort pulse using sum frequency generation (SFG), leaving an imprint of the spectral dispersion of the escort on the upconverted photon. Combined with an appropriate amount of dispersion on both the single photon and the escort beam, this time lens can stretch, compress, and invert the spectral and temporal waveforms of the photon. Using this temporal imaging technique to invert the spectral waveform of one photon in an entangled pair will reverse the spectral correlations between the entangled photons.
   
In this work, detailed in [5], we demonstrate control of a twin-photon joint spectral intensity through the use of an upconversion time lens on the ultrafast timescale. We measure a statistical correlation of −0.97 in the joint spectral intensity of an energy-time-entangled pair produced with SPDC, indicating strong frequency anti- correlations consistent with energy conservation found in traditional bulk SPDC sources. We apply a temporal imaging technique to the signal photon of the downconverted pair, and observe a strong positive statistical correlation of +0.86 between the untouched idler photon and the upconverted signal photon. We also show that the central frequency of the upconverted joint spectrum can be manipulated by introducing a time delay in the escort pulse. The technique presented is free of intense broadband noise at the target wavelengths. Control of the correlation of joint spectra as demonstrated in this work may be directly useful for shaping the spectra of entangled pairs for long-distance communications [2] and quantum-enhanced metrology [1] and, more generally, to mold the time-frequency distributions of entangled photons for experiments both fundamental and practical.

References:
[1] V. Giovannetti, S. Lloyd, L. Maccone, “Quantum-enhanced positioning and clock synchronization,” Nature 412, 417–419 (2001).
[2] W. P. Grice, A. B. U’Ren, I. A. Walmsley, “Eliminating frequency and space-time correlations in multiphoton states,” Phys. Rev. A 64, 063815 (2001).

Affiliation: Institute for Quantum Computing

Modelling the peak thermal conductivity of Dysprosium Titanate

Dysprosium titanate (Dy2Ti2O7 or DTO) is a key candidate for studying the thermal transport of magnetic monopoles due to its geometrically frustrated lattice. However, monopole thermal transport results differ depending on the peak thermal conductivity of the material. The height of this peak gives qualitative information about the number of lattice imperfections in each sample which can be quantified with modelling techniques. In this talk, I will discuss using the Callaway model of thermal conductivity to analyze the peak thermal conductivity of differing DTO samples.

Affiliation: University of Waterloo

The Optical Properties of Silicon Nanoparticles

Though silicon (Si) is a non-toxic and abundant semiconductor used extensively in the electronic and photovoltaic industries, the poor light emission of this material has stifled its use in optical and optoelectronic devices. The ability to use Si in such applications has many advantages that include low fabrication cost and high compatibility with existing technology. Therefore, there is a need to develop a Si-based light source by improving the light emission of Si, in order for Si to be used in such devices. In recent years, Si nanoparticles (Si-NPs) have been shown to be a promising candidate for developing such a light source.

The reason a Si-NP light emitting diode (LED) has yet to be produced is that although Si-NPs have greater light emission than bulk Si, the light produced by these NPs is still too low in intensity to be used in a commercial device. It is for this reason that we have explored various approaches for improving the luminescence of Si-NPs and for studying the mechanisms responsible for their luminescence. One such approach is to dope the matrix in which the Si-NPs are housed. We have observed an increase in the luminescence of Si-NPs embedded in silicon nitride when aluminum dopants are introduced via ion implantation and that this increase in internsity is dependent on dopant concentration.

Affiliation: Western University

When will a qubit's interaction show what shape it is inside?

Superconducting qubits operate via interaction with the electromagnetic field in highly tunable scenarios, making them ideal for experimental explorations of the light-matter interaction. The qubits are subject to a natural but uncharacterized ultraviolet cutoff---materials stop behaving as superconductors at high frequencies. The long-range nature of the interaction can be modeled as a spatial smearing. In a weak coupling regime, it is reasonable to assume a sharp ultraviolet cutoff and pointlike qubit.

As the strength of coupling increases, this assumption needs to be assessed.  We use the Unruh-DeWitt model in 1+1D to investigate the effect of the cutoff and smearing function on qubit dynamics using an experimentally realizable non-adiabatic switching function. We find that the cutoff is the primary contributor to the effective shape of the qubit and that, in an ideal scenario, the wrong choice of cutoff introduces significant noise.

This work was done in collaboration with Adrian Lupascu and Eduardo Martin-Martinez.

Affiliation:  Institute for Quantum Computing