Trapped ions and quantum optics side of life

  • Surface noise analysis using a single-ion sensor – 20 June 2014 (pdf here). The first ever experiment to combine a single-ion electric field noise sensor with in-situ surface treatment and surface analysis tools. Main finding: carbon contamination can cause high electric field noise levels near metal surfaces, but the presence of carbon contamination does not imply high noise.

  • Two-mode coupling in a single-ion oscillator via parametric resonance - 27 June 2014 (pdf here). In plain english: Imagine your two children are on two different swings, one swing is long, one is short -hence they swing at different frequencies. This method allows you to push only one of the swings and get both of your chidlren moving (works even for one child, swinging in two directions, each one being close to the quantum-mechanical ground state of motion!).

  • Quantum information processing with trapped electrons and superconducting electronics - 7 July 2013, (pdf here). You want your computer memory to be long-lived, fast, and scalable. The same properties are desirable for the quantum memory where the qubit states of a quantum information processsor will be stored. This work proposes a mechanism (the quantum version of a frequency mixer) and several architectures to achieve this using superconducting qubits and one of the most abundant particles: electrons.

  • Quantum Interfaces Between Atomic and Solid-State Systems - April 2013, (pdf here). Review article outlining the most important theoretical ideas and experimental challenges in building quantum devices which try to merge atom-optical and solid-state technologies. We pay particular attention to the importance of characteristic impedance of solid-state quantum buses.

  • Electric field compensation and sensing with a single ion in a planar trap - 1 December 2011, (pdf here). We use one of the smallest electric field sensors which are technologically available today (a single ion) to map the stray electrostatic field near a contaminated gold surface.

  • All that is gold does not glitter - 22 August 2011, (pdf here). The performance of ion traps suffers greatly from a source of noise that researchers had been unable to get rid of for more than 20 years. In the last 5 years or so, we did we start to get some hints on the causes of the noise (contaminated surfaces). This is our commentary on theoretical article which proposed a microscopic model for the noise.

  • Fabrication and heating rate study of microscopic surface electrode ion traps - 24 January 2011, (pdf here). Experiment showing that noise in ion traps can increase in vacuum, likely a contamination effecct. Also proposed a phenomenological model to explain the noise. One of the works which turned ion trappers’ attention to surface-related effects.

  • Wiring up trapped ions to study aspects of quantum information - 14 August 2009, (pdf here). Can you send quantum information (a quantum state) from one atom to another through a regular piece of wire? Simple estimates in this work showed that this is not only possible, but even feasible with current technology.

Vortices and superconductors side of life

  • Emergence of Quasi-Long-Range Order below the Bragg Glass Transition - 5 October 2007 (pdf here). To this day, we do not have a theory of melting (the destruction of long-range order) for three-dimensional solids. In this work, we studied how order develops in three dimensions, in superconducting vortex matter (think of it as entangled rice noodles, where the noodles are allowed to disentangle by tunneling through each other). We saw interesting hysteresis, and hints of phase coexistence.

  • Ewald construction and resolution function for rocking-curve small-angle neutron scattering experiments - October 2007, (pdf here). This work desscribes the mathematical framework which was used to analyze the experiments on “Emergence of Quasi-Long-Range Order”, and gives an easy to grasp geometrical interpretation.

  • Peak Effect in Polycrystalline Vortex Matter - 27 July 2007, (pdf here). By introducing defects (static disorder) to a crystal we can change its melting point. So, phase transitions are influenced by disorder, but what happens in the presence of very high levels of defects? Here we took this question to the extreme, by studying the order-disorder transition in a system with extreme level of static disorder: a polycrystalline superconducting alloy. We found that one signature of the order-disorder transition survived, despite the absence of signatures of macroscopic order in the system.

  • Magnetocaloric studies of the peak effect in Nb - 21 May 2007, (pdf here). Have you ever noticed how a can of spray cools down if you use it for a long time? Something similar happens to a superconductor (like niobium) when you change the magnetic field applied to it. By measuring the cooling effect, you can actually infer things about the amount of quantized magnetic flux tubes (the so-called vortices) which penetrate it. Here, we used this effect to study an order-disorder transition in the lattice that the vortices form in niobium.

PhD thesis

  • Experimental Studies of the Bragg Glass Transition in Niobium, May 2008. For my PhD work, I studied an order-disorder transition, in the presence of weak static disorder. I focused on two problems: Why the signature of the phase transition disappears in a surprising manner, and how order develops from the disordered phase. Both of these questions are still open, due to the loss of interest in the area of so-called “vortex physics”. I will rarely say this about my writings, but the introductory chapter to my thesis is always a source of inspiration for me to keep asking, keep learning, and keep undertanding.