Physics Department, Princeton University

Biophysics Seminar - Roman Stocker (MIT) "Spying on the lives of marine microbes: From biophysics to ecology "
At a time when microbial ecology is largely traveling along genomic roads, we cannot forget that the functions and services of microbes depend greatly on their behaviors, encounters, and interactions with their environment. New technologies, including microfluidics and high-speed video microscopy, provide a powerful opportunity to spy on the lives of microbes, directly observing their behaviors at the spatiotemporal resolution most relevant to their ecology, and enabling a deeper understanding of the biophysical mechanisms underpinning these behaviors. I will illustrate this 'quantitative natural history approach' to microbial ecology by focusing on marine bacteria, unveiling striking adaptations in their motility and chemotaxis and describing how these are connected to their incredibly dynamic, gradient-rich microenvironments. Specifically, I will present (i) sub-micrometer imaging of single cells at up to thousand frames per second, demonstrating that marine bacteria have a unique mode of swimming, exploiting a mechanical buckling instability of their flagellum to reorient; and (ii) microfluidic experiments that capture the dramatic chemotactic abilities of marine bacteria, including bacterial pathogens storming towards the roiling surface of their coral hosts. Through these examples, I aim to illustrate how we can use direct visualization to learn about the biophysical mechanisms and the ecological implications of the behaviors of the smallest of life forms.
Joseph Henry Room  ·  12:00 p.m.– 1:00 p.m.

Harnessing the Atom-like Properties of Single Spins in Diamond - Lee C. Bassett, Center for Spintronics and Quantum Computation, University of Califor
The past decade has seen remarkable progress in the isolation and control of single spins in solid state devices.  With electron spin coherence times in some materials now measured in seconds, single spins provide many features formerly unique to atomic systems in a form amenable to engineering complex integrated devices through semiconductor nanofabrication.  In particular, the nitrogen-vacancy (NV) center in diamond has emerged as a promising single-spin system for wide-ranging applications in quantum computing, quantum communication, and nanoscale sensing.  The NV center’s electronic spin can be initialized and measured optically, has millisecond coherence times at room temperature, and it provides access to individual nuclear spins with even better coherence properties. Recently, we have developed several techniques to control the NV center’s spin using coherent light-matter interactions – protocols that can be used to access other spin systems that lack the NV center’s unique optical addressability but might offer desirable properties for other applications. I will review the current state of this exciting field, describe several of our recent experiments, and outline the challenges and possibilities for the road ahead.
Jadwin A07  ·  12:15 p.m.– 1:15 p.m.

Condensed Matter Seminar - Andrew Sachrajda, The National Research Council - Coherent Behaviour in a Triple Quantum Dot Circuit
In this talk I will describe our experimental investigations of an AlGaAs/GaAs based triple quantum dot circuit and their comparison with theoretical models. We are able to employ both quantum transport and charge detection down to single electron/spin occupation and employ many of the pulsing techniques developed previously for two dot circuits. Our particular focus is the (1,1,1) regime in which a single spin occupies each quantum dot.  By varying pulse parameters we are able to observe coherent behaviour between specific three-spin levels including the DiVincenzo all-exchange qubit and various manifestations of Landau-Zener -Stückelberg oscillations and their interplay.  I will demonstrate the triple quantum dot equivalent of the double quantum dot Pauli blockade effect and show how in a linear triple quantum dot leakage currents can occur directly between edge dots via coherent quantum superpositions where the occupation of the center dot remains fixed. Finally I will demonstrate a quantum backaction process mediated via single phonon interferometry.  The figure below shows experimental LZS oscillations and the device layout used.

PCTS Seminar Room  ·  1:15 p.m.– 2:30 p.m.

High Energy Theory Seminar - Costis Papayeorgakis, Rutgers University - "On the (2,0) theory and 5D SYM"
"We will review the connection between the six-dimensional (2,0) theory and maximally supersymmetric Yang-Mills in five dimensions (MSYM). We will discuss the implications of a conjectured relation between the two, at all energy scales, for MSYM. We will also deconstruct MSYM from a four-dimensional circular quiver gauge theory and consider the possibility of instanton-solitons contributing to perturbative amplitudes."
PCTS Seminar Room  ·  2:30 p.m.– 3:30 p.m.