ITAMP News

April 8, 2021
Special ITAMP Seminars During the Pandemic

Taking the temperature of a pure quantum state

Temperature is a deceptively simple concept that still raises deep questions at the forefront of quantum physics research. The observation of thermalisation in completely isolated quantum systems, such as cold-atom quantum simulators, implies that a temperature can be assigned even to individual, pure quantum states. Here, we propose a scheme to measure the temperature of a pure state through quantum interference. Our proposal involves Ramsey interferometry of an auxiliary qubit probe, which is prepared in a superposition state and subsequently undergoes decoherence due to weak coupling with an isolated many-body system. Using only a few basic assumptions about chaotic quantum systems -- namely, the eigenstate thermalisation hypothesis and the equations of diffusive hydrodynamics -- we show that the qubit undergoes pure exponential decoherence at a rate that depends on the temperature of its surroundings. We verify our predictions by numerical experiments on a quantum spin chain that thermalises after absorbing energy from a periodic drive. Our work provides a general method to measure the temperature of isolated, strongly interacting systems under minimal assumptions.
Reference: https://arxiv.org/abs/2103.16601

Youtube:
https://youtu.be/h7LqxxYhmhc

April 3, 2021
Special ITAMP Seminars During the Pandemic
March 25, 2021
Special ITAMP Seminars During the Pandemic
March 11, 2021
Special ITAMP Seminars During the Pandemic
February 25, 2021
Special ITAMP Seminars During the Pandemic
January 29, 2021
The journal selected the paper for highlighting as an Editor's suggestion

The journal selected Nicole Yunger Halpern paper "Nonlinear Bell inequality for macroscopic measurements" for highlighting as an Editor's suggestion.
The quantum equivalent of seeing bacteria through everyday glasses
Entanglement—strong correlations that quantum particles can share— divides quantum physics from the everyday, or classical, world. Detecting entanglement in, for example, quantum computers and quantum networks is important: Only if nonclassical does a device have the potential to solve problems or to communicate information in ways impossible for today’s computers and telephones. Quantum systems are small, whereas classical systems are large. So conventional wisdom dictates that we can detect entanglement only if able to measure systems very precisely, similarly to how we can see bacteria only if given a microscope. This paper shows how to see bacteria through ordinary glasses, so to speak—how to detect entanglement amongst many particles by measuring only large-scale properties coarsely. The scheme works if the particles interact with each other in a limited fashion. Examples include detecting entanglement amongst photons (particles of light) by measuring the overall intensity of a beam of light. The photon proposal is testable in laboratories today; more- speculative applications include biochemistry and cosmology. This work challenges intuitions about the quantum-classical divide while helping us detect deviations from our everyday world.

November 2, 2020
The organizers of the ITAMP supported BlackInPhysics week in Physics Today

The organizers of the ITAMP supported BlackInPhysics week in Physics Today
(https://physicstoday.scitation.org/do/10.1063/PT.6.4.20201026b/full/)
Well done.

October 26, 2020
This week, Oct. 25-31 is BlackInPhysics week

This week, Oct. 25-31 is BlackInPhysics week. ITAMP is sponsoring this event.
You can check the status of activities here
(https://twitter.com/BlackinPhysics/status/1316506525964406785)
and here (blackinphysics.org).

October 22, 2020
Nicole Yunger Halpern won “International Quantum Technology Emerging Researcher Award”

Nicole Yunger Halpern, Postdoctoral Fellow at ITAMP, Center for Astrophysics, Harvard and Smithsonian, won “International Quantum Technology Emerging Researcher Award” from the Institute of Physics. The announcement appears at https://www.miragenews.com/iop-publishing-s-international-quantum-techno...

Her acceptance-speech video that records her thanks to ITAMP for its support https://youtu.be/_1KDyeKvqZo

August 24, 2020
Work done at ITAMP and CUA pave the way to increasing the lifetimes of ultracold trapped molecules

You may access the article through the link below:

https://physics.aps.org/articles/v13/s100

August 17, 2020
ITAMP Fellow Nicole Yunger Halpern and colleagues publish quantum-metrology paper in Nature Communications

Researchers including ITAMP Fellow Nicole Yunger Halpern recently proved that quantum physics can enhance metrology, if a simple extra measurement is performed during an experiment. The proof technique hinges on mathematical objects that resemble probabilities but that can assume negative values when describing quantum systems. The result was published in Nature Communications and featured in a news article by the University of Cambridge:

https://www.cam.ac.uk/research/news/quantum-negativity-can-power-ultra-p...

August 10, 2020
A new memoir of Alex Dalgarno on the fifth anniversary of his death, by two of his former students

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