News
My PhD student, Jesús Mateos (co-supervised with Fernando Sols) was awarded his PhD cum laude on the 14th of March, for his thesis "Superfluidez correlacionada y caos cuántico en un gas de bosones conducido periódicamente en el tiempo". Congratulations to the new Dr Mateos!
Sierpinski's gasket is a fractal built recursively from triangles, with a Hausdorff dimension of ~1.585. Suppose one builds a network of resistors following this scheme - how will the resistance scale as the level of recursion increases? Is this scaling related to the shape's fractal dimension?
I studied this question in a paper published in The Physics Teacher. The results show the beautiful way in which the resistance of a finite network network of resistors has a power-law scaling, which indeed is related to the Sierpinski gasket's dimension. The work is also the subject of a Scilight "Fractals and resistors run in parallel in the classroom."
Back in 2014 German Sierra and I showed how the zeros of the Riemann function could be observed in the Floquet spectrum of a system, driven with the correct time-dependent function. In early 2021 the experimental ion-trap group in Hefei, China used this scheme to measure the first three non-trivial zeros of the zeta function: Phys. Rev. A. By developing an improved form of the driving function, this was later extended to measuring the first 80 zeros! This has now been published in the Nature Partner Journal: Quantum Information.
Juan Zurita carried out a TFG project with me and Gloria Platero over the academic year 2018 - 2019, funded by a beca de colaboracion. This research has been awarded a prize for "Student Research" by the División de Física de la Materia Condensada (GEFES) of the RSEF (Spanish Physical Society). Well done Juan!
A write-up of the research, "Topology and Interactions in the Photonic Creutz and Creutz-Hubbard Ladders" is available here, and it has now been published in Advanced Quantum Technologies.
Juan gave a talk on this subject at PLMCN2020. You can see it here.
My PhD student, Greg Pieplow (co-supervised with Fernando Sols) was awarded his PhD cum laude on the 19th of September, for his thesis "Exotic quantum matter generated from Floquet engineering". Congratulations to the new Dr Pieplow!
The latest paper from our research group, "Protected cat states from kinetic driving of a boson gas", has been published by Physical Review Research. Here is the "Teaser":
Fast driving of the hopping energy with zero time-average ("kinetic driving") of bosons in an optical lattice results in an exotic effective time-independent Hamiltonian, whose ground state is a protected cat state. The two cat branches preferentially occupy modes with momenta $\pm \pi/2$, while sharing a small reduction cloud of unusually paired momenta, which contributes to the protection. The resulting system is superfluid despite the absence of first-order single-particle hopping.
Two-particle momentum density, showing the formation of a cat state.
Older news:
Airy wavepacket paper accepted for publication!
What happens when particles move at high speeds, comparable to the speed of light? Classically the result is well-known; the standard equations of Newtonian mechanics evolve into the those given by special relativity. If one is studying a non-relativistic quantum mechanical system, one can ask the corresponding question of how relativity will come into play as the velocity of the particle increases. How does the system pass into the relativistic regime?
The Airy wavepacket is a particular solution of the Schrodinger equation that has a very unusual property; quantum interference effects cause it to undergo a constant acceleration. It should thus eventually become relativistic when its velocity becomes similar to the speed of light. This can be studied conveniently by confining it to move in a lattice potential. The lattice provides a natural "speed limit" given by the system's maximum group velocity, which can be many orders of magnitude lower than the true speed of light.
In this paper I show that an Airy wavepacket moving in a lattice is indeed described by relativisitic equations, and how Floquet engineering can be used to control it. Surprisingly, relativistic motion can simply arise from the standard (non-relativistic) Schrodinger equation!
The 8th Madrid Meeting on Cold Atoms was held at the Universidad Complutense on Monday, 11th of January 2016. The next meeting will be hosted by the Universidad Autónoma de Madrid.
Previous meetings in this series:
7th Meeting (October 2014), CSIC Serrano
6th Meeting (January 2014), Universidad Autónoma de Madrid
5th Meeting (June 2013), Universidad Complutense de Madrid
4th Meeting (January 2013), CSIC Serrano
Third Meeting (June 2012), Universidad Autónoma de Madrid
Second Meeting (December 2011), Universidad Complutense de Madrid
First meeting (May 2011), CSIC Serrano
More details here
Our paper on using shaken optical lattices to create a synthetic magnetic field for cold atoms has now been published in Phys. Rev. A.
My PhD student, Martin Heimsoth (co-supervised with Fernando Sols) made his thesis defence on the 1st of July. Congratulations to the new Dr Heimsoth!
Our paper on the "orbital Josephson effect" has been published in the New Journal of Physics. Read the article, or watch a video abstract prepared by my student Martin Heimsoth.