Applied Physics / Physics Colloquium

AP 483 Seminar presents "Benchmarking quantum computers and future directions for superconducting quantum hardware"

Topic: 
Benchmarking quantum computers and future directions for superconducting quantum hardware
Abstract / Description: 

While the fully fault-tolerant universal quantum computing system is still many years ahead, building an early quantum computer with quantum advantage becomes a feasible near-term milestone that we can realistically plan. Increasing number of near-term applications has been accelerating the development of quantum hardware in the industries, and as quantum system size grows, we need a whole system metric to evaluate the level of hardware performance. I would like to introduce the quantum volume (arXiv:1811.12926 and more recently arXiv:2008.08571) as a system-level metric that quantifies quantum computational power of early quantum computing processors. The quantum volume depends on various individual component metrics such as gate fidelity and crosstalk. I will discuss some of the challenges in building superconducting quantum hardware and suggest few directions to improve the quantum volume.


This seminar is sponsored by the department of Applied Physics and the Ginzton Laboratory.

Date and Time: 
Monday, November 2, 2020 - 4:15pm

AP 483 Seminar presents "Quantum Technologies Enabled by Cavity-Optomechanics at Low Temperatures"

Topic: 
Quantum Technologies Enabled by Cavity-Optomechanics at Low Temperatures
Abstract / Description: 

The ability to fabricate devices that demonstrate quantum behavior, as opposed to being restricted to what nature has given us, has opened up the possibility of technologies based on the laws of quantum physics instead of classical physics. The prime example of this is the superconducting qubit at the core of a quantum processor. Another class of fabricated devices that are beginning to demonstrate quantum behavior is that of nanoscale mechanical resonators. Such devices promise force and torque sensors operating at or beyond the standard quantum limit, and novel technologies such as quantum-level wavelength transducers. I will tell you about our efforts to develop such technologies and some of the fun physics we have uncovered along the way.


This seminar is sponsored by the department of Applied Physics and the Ginzton Laboratory.

Date and Time: 
Monday, October 26, 2020 - 4:15pm
Venue: 
Zoom

AP 483 Seminar presents "Organic small molecule integrated photonics"

Topic: 
Organic small molecule integrated photonics
Abstract / Description: 

The initial, landmark integrated photonic devices relied on silicon and III-V materials, and recent advances in material fabrication and deposition methods have enabled a plethora of new technologies based on materials with higher optical nonlinearities, including 2D materials and organic polymers. However, nonlinear optical (NLO) organic small molecules have not experienced similar growth due to a perceived environmental instability and to challenges related to intra and intermolecular interactions. Because NLO small molecules have NLO coefficients that are orders of magnitude larger than conventional optical materials, developing strategies to fabricate optical devices could enable significant performance improvements. In recent work, we combined conventional top-down fabrication methods with bottom-up techniques to develop on-chip devices that incorporated NLO optical small molecules. These hybrid systems provide access to optical behavior and performance not attainable with conventional material systems. In this seminar, I will discuss a couple examples of NLO small molecule integrated resonators, including Raman lasers and all optically-switchable devices.


This seminar is sponsored by the department of Applied Physics and the Ginzton Laboratory.

Date and Time: 
Monday, October 19, 2020 - 4:15pm

AP 483 Seminar presents "Spin-photon interfaces for quantum networks"

Topic: 
Spin-photon interfaces for quantum networks
Abstract / Description: 

Spin-photon interfaces augmented with auxiliary qubits are prime candidates for quantum repeater nodes. I will present our theoretical work toward the realization of practical quantum repeaters, focusing on the triggered generation of highly entangled photonic (graph) states from a spin-photon interface and their performance-resource tradeoff in a network. I will also discuss our quantum control work on the selective high-fidelity control of a nuclear spin register coupled to an NV center spin in diamond.


This seminar is sponsored by the department of Applied Physics and the Ginzton Laboratory.

Date and Time: 
Monday, October 12, 2020 - 4:15pm

AP 483 Seminar presents "A Renaissance in Brillouin scattering"

Topic: 
A Renaissance in Brillouin scattering
Abstract / Description: 

Brillouin scattering was for many years confined to experiments in hundreds of metres of optical fibre, in which the spectrum was fixed and where Brillouin properties were almost identical to those of bulk materials. A recent renaissance in Brillouin scattering research has been driven by the increasing maturity of photonic integration platforms as well as advances in nanophotonics and nonlinear optics. A central problem to be solved in integrated applications has been the simultaneous confinement of the optical and acoustic waves. Traditional silicon nanowires confine light but do not confine sound and the group IV semiconductors are typically very stiff so that rib waveguides do not guide elastic waves. A first solution to the confinement problem, and the first demonstration of SBS in an integrated photonic environment, was found in the chalcogenide soft glass platform, where the high refractive index and low stiffness of As2Se3 glass allowed for confinement of both optical and elastic waves by total internal reflection, leading to strong Brillouin gain and a multitude of application possibilities. I will review the diverse array of strategies that have been used to enhance and shape Brillouin interactions within integrated photonic waveguide systems, as well as some of the goals and motivations of the growing field of integrated Brillouin photonics with particular emphasis on my group's research on developing compact microwave photonic functions.


 

This seminar is sponsored by the department of Applied Physics and the Ginzton Laboratory.

Date and Time: 
Monday, October 5, 2020 - 4:15pm

Applied Physics/Physics Colloquium presents "New roles for wormholes"

Topic: 
New roles for wormholes
Abstract / Description: 

A powerful idea in theoretical physics is the conjecture that (from a distance) black holes behave like ordinary quantum systems. Thought of in this way, black holes display many deep quantum phenomena in simple but often surprising ways. We will discuss recent work (involving wormholes) that gives new examples of this and also uncovers new puzzles.

Date and Time: 
Tuesday, May 5, 2020 - 4:30pm
Venue: 
Zoom Meeting ID: 954 8449 2474

Q-Farm Quantum Seminar Series presents "Surprises from Time Crystals"

Topic: 
Surprises from Time Crystals
Abstract / Description: 

Time crystals are new states of matter that only exist in an out-of-equilibrium setting. I will review the state of this rapidly evolving field, focusing in particular on some of the remarkable properties of this phase, and the surprises coming out of its study. I will provide a detailed overview of existing experiments, with a view towards identifying the ingredients needed for an unambiguous observation of this phase in the future.

Date and Time: 
Wednesday, January 29, 2020 - 12:00pm
Venue: 
Hansen Physics & Astrophysics Building, 102/103

Applied Physics/Physics Colloquium: Quantum Optical Control of Levitated Solids: a novel probe for the gravity-quantum interface

Topic: 
Quantum Optical Control of Levitated Solids: a novel probe for the gravity-quantum interface
Abstract / Description: 

The increasing level of control over motional quantum states of massive, solid-state mechanical devices opens the door to a hitherto unexplored parameter regime of macroscopic quantum physics. I will report on our recent progress towards controlling levitated solids in the quantum regime. I will discuss the prospects of using these systems for fundamental tests of physics, including the interface between quantum and gravitational physics.


Winter Qtr. Colloq. committee: M. Schleier-Smith (Chair), B. Cabrera, S. Dimopoulos, T. Heinz, S. Kachru & L. Tompkins
Location: Hewlett Teaching Center, Rm. 200

Date and Time: 
Tuesday, March 3, 2020 - 4:30pm
Venue: 
Hewlett 200

Applied Physics/Physics Colloquium presents "Dark Matter halos from parametric resonance and their signatures"

Topic: 
Dark Matter halos from parametric resonance and their signatures
Abstract / Description: 

While there is undisputed evidence for Dark Matter, its nature and properties remain one of the biggest questions of our time. What is Dark Matter (DM)? How is it produced? Does it have interactions other than gravitational? In this talk, I will describe how a large class of bosonic particles can account for the DM of the Cosmos. These particles can be much lighter than those of the Standard Model with Compton wavelengths that are bigger than the size of our solar system or smaller than a millimeter. In the presence of attractive self-interactions, there is a parametric resonance effect in the early universe that can cause growth of structure at small scales, an effect so dramatic that can cause structures to collapse well before matter-radiation equality. The signatures of this effect span several experiments and orders of magnitude in parameter space. When the DM boson is heavy, the dense DM halos can alter the optimal search strategies in direct detection experiments. When the DM boson is light, these halos may leave their imprint in searches for dark matter substructure, primordial gravitational waves and alter the star formation history of the universe.


Winter Qtr. Colloq. committee: M. Schleier-Smith (Chair), B. Cabrera, S. Dimopoulos, T. Heinz, S. Kachru & L. Tompkins
Location: Hewlett Teaching Center, Rm. 200

Date and Time: 
Tuesday, February 25, 2020 - 4:30pm
Venue: 
Hewlett 200

Applied Physics/Physics Colloquium presents "Fracton – elasticity duality"

Topic: 
Fracton – elasticity duality
Abstract / Description: 

I will discuss a recent discovery that elasticity theory of a two-dimensional quantum crystal is dual to a fracton tensor and to a coupled-vector gauge theories, thereby providing a concrete realization of the so-called "fracton quantum order". The disclinations and dislocations respectively map onto charges and dipoles of these gauge theories. The fractionalized mobility of fractons matches the constrained dynamics of crystal's topological defects. These dualities lead to predictions of fractonic phases, and phase transitions to their descendants, that are duals of the commensurate crystal, supersolid, smectic, and hexatic liquid crystals. Extensions of this duality to generalized elasticity theories provide a route to discovery of new fractonic models and their potential experimental realizations.


Winter Qtr. Colloq. committee: M. Schleier-Smith (Chair), B. Cabrera, S. Dimopoulos, T. Heinz, S. Kachru & L. Tompkins
Location: Hewlett Teaching Center, Rm. 200

Date and Time: 
Tuesday, February 18, 2020 - 4:30pm
Venue: 
Hewlett 200

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