Applied Physics / Physics Colloquium

Protecting Quantum Superpositions in Superconducting Circuits [Applied Physics/Physics Colloquium]

Topic: 
Protecting Quantum Superpositions in Superconducting Circuits
Abstract / Description: 

Can we prolong the coherence of a two-state manifold in a complex quantum system beyond the coherence of its longest-lived component? This question is the starting point in the construction of a scalable quantum computer. It translates in the search for processes that operate as some sort of Maxwell's demon, reliably correcting the errors resulting from the coupling between qubits and their environment. The presentation will review recent experiments that tested the dynamical protection, by Josephson circuits, of a logical qubit memory based on superpositions of particular coherent states of a superconducting resonator.


 

APPLIED PHYSICS/PHYSICS COLLOQUIUM

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 200. Refreshments in the lobby of Varian Physics at 4:15 pm.

Winter 2016/2017, Committee: A. Linde (Chair), S. Kivelson, S. Zhang

Date and Time: 
Tuesday, May 30, 2017 - 4:15pm
Venue: 
Hewlett 200

Coherent Defects in Diamond [Applied Physics/Physics Colloquium]

Topic: 
Coherent Defects in Diamond
Abstract / Description: 

Engineering coherent systems is a central goal of quantum science and quantum information processing. Point defects in diamond known as color centers are a promising physical platform. As atom-like systems, they can exhibit excellent spin coherence and can be manipulated with light. As solid-state defects, they can be produced at high densities and incorporated into scalable devices. Diamond is a uniquely excellent host: it has a large band gap, can be synthesized with sub-ppb impurity concentrations, and can be isotopically purified to eliminate magnetic noise from nuclear spins. Specifically, the nitrogen vacancy (NV) center has been used to has been used to demonstrate basic building blocks of quantum networks and quantum computers, and has been demonstrated to be a highly sensitive, non-invasive magnetic probe capable of resolving the magnetic field of a single electron spin with nanometer spatial resolution. However, realizing the full potential of these systems requires the ability to both understand and manipulate diamond as a material. I will present two recent results that demonstrate how carefully tailoring the diamond host can dramatically improve the performance of color centers for various applications.

First, currently-known color centers either exhibit long spin coherence times or efficient, coherent optical transitions, but not both. We have developed new methods to control the diamond Fermi level in order to stabilize a new color center, the neutral charge state of the silicon vacancy (SiV) center, which exhibits both the excellent optical properties of the negatively charged SiV center and the long spin coherence times of the NV center, making it a promising candidate for applications as a single atom quantum memory for long distance quantum communication.

Second, color centers placed close to the diamond surface can have strong interactions with molecules and materials external to the diamond. However, uncontrolled surface termination and contamination can degrade the color center properties and give rise to noise that obscures the signal of interest. I will describe our recent efforts to stabilize shallow NV centers within 5 nm of the surface using new surface processing and termination techniques. These highly coherent, shallow NV centers will provide a platform for sensing and imaging down to the scale of single atoms.


 

APPLIED PHYSICS/PHYSICS COLLOQUIUM

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 200. Refreshments in the lobby of Varian Physics at 4:15 pm.

Winter 2016/2017, Committee: A. Linde (Chair), S. Kivelson, S. Zhang

Date and Time: 
Tuesday, May 23, 2017 - 4:15pm
Venue: 
Hewlett 200

Morphogenesis: Geometry, Physics and Biology [Applied Physics/Physics Colloquium]

Topic: 
Morphogenesis: Geometry, Physics and Biology
Abstract / Description: 

A century after the publication of D'Arcy Thompson's eponymous classic, "On growth and form," his vision has finally begun to permeate into the fabric of modern biology. Within this backdrop, I will discuss the geometry and physics of biological morphogenesis, with a particular focus on regulated differential growth, using examples from a range of scales: macromolecular assemblies, single cells, and multicellular tissues. Along the way, I will also discuss aspects of morphometries, the quantification of biological shape, and morphogramming, the design of bioinspired shape.


 

APPLIED PHYSICS/PHYSICS COLLOQUIUM

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 200. Refreshments in the lobby of Varian Physics at 4:15 pm.

Winter 2016/2017, Committee: A. Linde (Chair), S. Kivelson, S. Zhang

Date and Time: 
Tuesday, May 16, 2017 - 4:15pm
Venue: 
Hewlett 200

New Probes of Old Structure: Cosmology with 21cm Intensity Mapping and the Cosmic Microwave Background [Applied Physics/Physics Colloquium]

Topic: 
New Probes of Old Structure: Cosmology with 21cm Intensity Mapping and the Cosmic Microwave Background
Abstract / Description: 

Current cosmological measurements have left us with deep questions about our Universe: What caused the expansion of the Universe at the earliest times? How did structure form? What is Dark Energy and does it evolve with time? New experiments like CHIME, HIRAX, and ACTPol are poised to address these questions through 3-dimensional maps of structure and measurements of the polarized Cosmic Microwave Background. In this talk, I will describe how we will use 21cm intensity measurements from CHIME and HIRAX to place sensitive constraints on Dark Energy between redshifts 0.8 -- 2.5, a poorly probed era corresponding to when Dark Energy began to impact the expansion history of the Universe. I will also discuss how we will use data from new instruments on the ACT telescope to constrain cosmological parameters like the total neutrino mass and probe structure at late times.


 

APPLIED PHYSICS/PHYSICS COLLOQUIUM

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 200. Refreshments in the lobby of Varian Physics at 4:15 pm.

Winter 2016/2017, Committee: A. Linde (Chair), S. Kivelson, S. Zhang

Date and Time: 
Tuesday, May 9, 2017 - 4:15pm
Venue: 
Hewlett 200

A Research-validated Approach to Transforming upper-division Physics Courses [Applied Physics/Physics Colloquium]

Topic: 
A Research-validated Approach to Transforming upper-division Physics Courses
Abstract / Description: 

TBA


 

APPLIED PHYSICS/PHYSICS COLLOQUIUM

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 200. Refreshments in the lobby of Varian Physics at 4:15 pm.

Winter 2016/2017, Committee: A. Linde (Chair), S. Kivelson, S. Zhang

Date and Time: 
Tuesday, May 2, 2017 - 4:15pm
Venue: 
Hewlett 200

Humanity's First Interstellar Mission [Applied Physics/Physics Colloquium]

Topic: 
Humanity's First Interstellar Mission
Abstract / Description: 

All propulsion systems that leave the Earth are based on chemical reactions with a few adding ion engines. Chemical reactions, at best, have an efficiency compared to rest mass of 10-9 (or about 1eV per bond). All the mass in the universe converted to chemical reactions would not propel even a single proton to relativistic speeds. While chemistry will get us to Mars, it will not allow interstellar capability in any reasonable mission time. Barring new physics, we are left with few solutions, other than science fiction and imaginary propulsion. Recent advances in photonics and directed energy systems now allow us to realize the possibility of relativistic flight. With spacecraft from fully-functional gram-level wafer-scale systems ("wafer sats") capable of speeds greater than c/4 that could reach the nearest star in 20 years to spacecraft for large missions capable of supporting human life with masses more than 105 kg (100 tons) for rapid interplanetary transit that could reach speeds of greater than 1000 km/s can be realized. With this technology spacecraft can be propelled to speeds currently unimaginable. Photonics, like electronics, and unlike chemical propulsion is an exponential technology with a current double time of about 20 months. It is this that is the key. In addition, the same photon driver can be used for many other purposes such as planetary defense, space debris vaporization and de-orbiting, beaming energy to distant spacecraft, beaming power for high Isp ion engine missions, asteroid mining, sending power back to Earth for high value needs, stand-off composition analysis, long range laser communications, SETI searches, kilometer class telescopes among others. This would be a profound change in human capability, one whose non-scientific implications would be enormous. Known as Starlight, NASA began our Phase I funding in April 2015. On April 12, 2016 the Breakthrough Foundation announced that they would support this effort with a 100M$ Research and Development program called Breakthrough Starshot that would explore the fundamental technology underlying this. On May 12, 2016 NASA announced Phase II funding. On May 23 the FY 2017 congressional appropriations request directs NASA to study the feasibility of an interstellar mission to coincide with the 100th anniversary of the moon landing using quoting our NASA program as one option. I will discuss the idea of relativistic flight generally, the many technical challenges ahead, our current laboratory prototypes and data as well as the transformative implications of this program.


 

APPLIED PHYSICS/PHYSICS COLLOQUIUM

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 200. Refreshments in the lobby of Varian Physics at 4:15 pm.

Winter 2016/2017, Committee: A. Linde (Chair), S. Kivelson, S. Zhang

Date and Time: 
Tuesday, April 25, 2017 - 4:15pm
Venue: 
Hewlett 200

In Search of Cosmic-Ray Antinuclei from Dark Matter [Applied Physics/Physics Colloquium]

Topic: 
In Search of Cosmic-Ray Antinuclei from Dark Matter
Abstract / Description: 

Cosmic-ray antiprotons have been a valuable tool for dark matter searches since the 1970's. Recent years have seen increased theoretical and experimental effort towards the first-ever detection of cosmic-ray antideuterons, in particular as an indirect signature of dark matter annihilation or decay in the Galactic halo. In contrast to other indirect detection signatures, which have been hampered by the large and uncertain background rates from conventional astrophysical processes, low-energy antideuterons provide an essentially background-free signature of dark matter, and low-energy antiprotons are a vital partner for this analysis. I will discuss the currently planned or ongoing experiments that will be sensitive to antideuteron flux levels predicted for dark matter, focusing on the balloon-borne GAPS experiment, which exploits a novel detection technique utilizing exotic atom capture and decay to provide both a sensitive antideuteron search and a precision antiproton measurement in an unprecedented low-energy range. I will finish by looking ahead to the tantalizing prospect of cosmic antihelium measurements, as a probe of both cosmic-ray and dark matter physics.

Date and Time: 
Tuesday, April 18, 2017 - 4:15pm
Venue: 
Hewlett 200

Controlling and Exploring Quantum Matter Using Ultracold Atoms in Optical Lattices [Applied Physics/Physics Colloquium]

Topic: 
Controlling and Exploring Quantum Matter Using Ultracold Atoms in Optical Lattices
Abstract / Description: 

More than 30 years ago, Richard Feynman outlined the visionary concept of a quantum simulator for carrying out complex physics calculations. Today, his dream has become a reality in laboratories around the world. In my talk I will focus on the remarkable opportunities offered by ultracold quantum gases trapped in optical lattices to address fundamental physics questions ranging from condensed matter physics over statistical physics to high energy physics with table-top experiment.

For example, I will show how it has now become possible to image and control quantum matter with single atom sensitivity and single site resolution, thereby allowing one to directly image individual quantum fluctuations of a many-body system, to directly reveal antiferromagnetic order in the fermionic Hubbard model or hidden 'topological order'. I will also show, how recent experiments with cold gases in optical lattices have enabled to realise and probe artificial magnetic fields that lie at the heart of topological energy bands in a solid, including Thouless charge pumps in multiple dimensions. Finally, I will discuss our recent experiments on novel many-body localised states of matter that challenge our understanding of the connection between statistical physics and quantum mechanics at a fundamental level.

Date and Time: 
Tuesday, April 11, 2017 - 4:30pm
Venue: 
Hewlett 200

Presence of Quantum Diffusion in Two Dimensions [Applied Physics/Physics Colloquium]

Topic: 
Presence of Quantum Diffusion in Two Dimensions
Abstract / Description: 

All condensed matter systems possess disorder and interaction effects. Still, the qualitative effects of disorder and interactions in quantum systems are poorly understood. This is especially true when it comes to electrical conduction. The standard theory, developed for non-interacting particles over 40 years ago, predicted surprisingly that for the most part, disorder destroys metallic behavior in two-dimensional (2d) systems at zero temperature. For many decades, this "absence of quantum diffusion in 2d" was taken to be scientific law. However, with strong interactions, there is no reason to believe that this dogma survives.

I will review the experiments that have challenged this conventional wisdom, and will describe ongoing theoretical efforts to establish that metallic ground states can occur in 2d due to strong interaction effects.

Date and Time: 
Tuesday, April 4, 2017 - 4:30pm
Venue: 
Hewlett 200

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