Publications Milena GUEVARA-BERTSCH

2021

Article

M. I. Hussain, D. Heinrich, M. Guevara-Bertsch, E. Torrontegui, J. J. Garcia-Ripoll, C. F. Roos, R. Blatt Ultraviolet Laser Pulses with Multigigahertz Repetition Rate and Multiwatt Average Power for Fast Trapped-Ion Entanglement Operations, Phys. Rev. Applied 15 24054 (2021-02-23), http://dx.doi.org/10.1103/PhysRevApplied.15.024054 doi:10.1103/PhysRevApplied.15.024054 (ID: 720517) Toggle Abstract
The conventional approach to perform two-qubit gate operations in trapped ions relies on exciting the ions on motional sidebands with laser light, which is an inherently slow process. One way to implement a fast entangling gate protocol requires a suitable pulsed laser to increase the gate speed by orders of magnitude. However, the realization of such a fast entangling gate operation presents a big technical challenge, as such the required laser source is not available off-the-shelf. For this, we have engineered an ultrafast entangling gate source based on a frequency comb. The laser generates bursts of several hundred mode-locked pulses with pulse energy ∼800 pJ at 5 GHz repetition rate at 393.3 nm and complies with all requirements for implementing a fast two-qubit gate operation. To verify the applicability and projected performance we run simulations based on our source parameters. The gate time can be faster than a trap period with an error approaching 10^(−4).

2019

Articles

D. Heinrich, M. Guggemos, M. Guevara-Bertsch, M. I. Hussain, C. F. Roos, R. Blatt Ultrafast coherent excitation of a Ca+ ion, New J. Phys. 21 83025 (2019-07-01), http://dx.doi.org/10.1088/1367-2630/ab2a7e doi:10.1088/1367-2630/ab2a7e (ID: 720108) Toggle Abstract
Trapped ions are a well-studied and promising system for the realization of a scalable quantum computer. Faster quantum gates would greatly improve the applicability of such a system and allow for greater flexibility in the number of calculation steps. In this paper we present a pulsed laser system, delivering picosecond pulses at a repetition rate of 5 GHz and resonant to the S1/2 to P3/2 transition in Ca+ for coherent population transfer to implement fast phase gate operations. The optical pulse train is derived from a mode-locked, stabilized optical frequency comb and inherits its frequency stability. Using a single trapped ion, we implement three different techniques for measuring the ion-laser coupling strength and characterizing the pulse train emitted by the laser, and show how all requirements can be met for an implementation of a fast phase gate operation.
M. Guggemos, M. Guevara-Bertsch, D. Heinrich, Ó. A. Herrera, Y. Colombe, R. Blatt, C. F. Roos Frequency measurement of the 1S0,F=5/2 to 3P1,F=7/2 transition of 27Al+ via quantum logic spectroscopy with 40Ca+, New J. Phys. 21 103003 (2019-04-25), http://dx.doi.org/10.1088/1367-2630/ab447a doi:10.1088/1367-2630/ab447a (ID: 720264) Toggle Abstract
We perform quantum logic spectroscopy with a 27Al+/40Ca+ mixed ion crystal in a linear Paul trap for a measurement of the (3s2)1S0 to (3s3p)3P1,F=7/2 intercombination transition in 27Al+. Towards this end, Ramsey spectroscopy is used for probing the transition in 27Al+ and the (4s2)S1/2 to (4s3d)D5/2 clock transition in 40Ca+ in interleaved measurements. By using the precisely measured frequency of the clock transition in 40Ca+ as a frequency reference, we determine the frequency of the intercombination line to be 1S0 to 3P1,F=7/2=1122 842 857 334 736(93) Hz and the Landé g-factor of the excited state to be g3P1,F=7/2=0.428132(2).

2018

Article

M. Guevara-Bertsch, A. Chavarría-Sibaja, A. Godínez-Sandí, O. Herrera-Sancho Energy exchange between atoms with a quartz crystal μ-balance, New J. Phys. 20 123001 (2018-12-05), http://dx.doi.org/10.1088/1367-2630/aaf117 doi:10.1088/1367-2630/aaf117 (ID: 720163) Toggle Abstract
We propose an experimental method to fully characterize the energy exchange of particles during the physical vapor deposition (PVD) process of thin surface layers. Our approach is based on the careful observation of perturbations of the oscillation frequency of a quartz crystal μ-balance induced by the particles' interaction. With this technique it is possible to measure the momentum exchange of the atoms during the evaporation process and determine the ideal evaporation rate for uniform energy distribution. We are able to follow the desorption dynamics of particles' immediately after the first layers have been formed. These results are in close relation to the surface binding energy of the evaporated material and offer a better control to obtain the desired properties of the thin surface layer. The novelty of our work consists of the demonstration that quartz crystal μ-balance can be successfully implemented to monitor complex dynamics through the energy interaction of particles during PVD. We applied our technique to investigate the PVD mechanism for diverse elements, usually implemented in the development of film surface layers, such as Cu, W, Au, Gd and In, and confirm that our results are in agreement with measurements done previously with other techniques such as low temperature photo-luminescence.