arXiv subjects

Rodrigo González Escudero

Publications and source records attributed to Rodrigo González Escudero.

6 recordsLinked to original sources

arXiv2024

Ultrastable optical frequency dissemination over a branching passive optical network using CDMA

We demonstrate a technique for ultrastable optical frequency dissemination in a branching passive optical network using code-division multiple access (CDMA). In our protocol, each network user employs a unique pseudo-random sequence to rapidly change the optical frequency among many distinct frequencies. After transmission through the optical network, each user correlates the received sequence with the transmitted one, thus establishing a frequency-hopping spread spectrum technique that helps reject optical signals transmitted by other users in the network. Our method, which builds on the work by Schediwy et al. [Opt. Lett. {\bf 38}, 2893 (2013)], improves the frequency distribution network's capacity, helps reject phase noise caused by intermediate optical back scattering, and simplifies the operational requirements. Using this protocol, we show that a frequency instability better than ~$10^{-18}$ while having more than 100 users operating in the network should be possible. Finally, we theoretically explore the limits of this protocol and show that the demonstrated stability does not suffer from any fundamental limitation. In the future, the CDMA method presented here could be used in complex time-frequency distribution networks, allowing more users while, at the same time, reducing the network's complexity.

physics.optics↗

arXiv2024

Optical pumping of ${\mathrm{5s4d} ^1\mathrm{D}_2}$ strontium atoms for laser cooling and imaging

We present a faster repumping scheme for strontium magneto-optical traps operating on the broad ${\mathrm{5s^2} ^1\mathrm{S}_0} - {\mathrm{5s5p} ^1\mathrm{P}_1}$ laser cooling transition. Contrary to existing repumping schemes, we directly address lost atoms that spontaneously decayed to the ${\mathrm{5s4d} ^1\mathrm{D}_2}$ state, sending them back into the laser cooling cycle by optical pumping on the ${\mathrm{5s4d} ^1\mathrm{D}_2} - {\mathrm{5s8p} ^1\mathrm{P}_1}$ transition. We thus avoid the $\sim 100 \, \mathrm{μs}$-slow decay path from ${\mathrm{5s4d} ^1\mathrm{D}_2}$ to the ${\mathrm{5s5p} ^3\mathrm{P}_{1,2}}$ states that is part of other repumping schemes. Using one low-cost external-cavity diode laser emitting at $448 \, \mathrm{nm}$, we show our scheme increases the flux out of a 2D magneto-optical trap by $60 \, \%$ compared to without repumping. Furthermore, we perform spectroscopy on the ${\mathrm{5s4d} ^1\mathrm{D}_2} - {\mathrm{5s8p} ^1\mathrm{P}_1}$ transition and measure its frequency $ν_{\mathrm{^{88}Sr}} = (668917515.3 \pm 4.0 \pm 25) \, \mathrm{MHz}$. We also measure the frequency shifts between the four stable isotopes of strontium and infer the specific mass and field shift factors, $δν_\text{SMS} ^{88,86} = -267(45) \, \mathrm{MHz}$ and $δν_\text{FS} ^{88,86} = 2(42) \, \mathrm{MHz}$. Finally, we measure the hyperfine splitting of the ${\mathrm{5s8p} ^1\mathrm{P}_1}$ state in fermionic strontium, and deduce the magnetic dipole and electric quadrupole coupling coefficients $A = -4(5) \, \mathrm{MHz}$ and $B = 5(35) \, \mathrm{MHz}$. Our experimental demonstration shows that this simple and very fast scheme could improve the laser cooling and imaging performance of cold strontium atom devices, such as quantum computers based on strontium atoms in arrays of optical tweezers.

physics.atom-ph↗

arXiv2021

Continuous Bose-Einstein condensation

Bose-Einstein condensates (BECs) are macroscopic coherent matter waves that have revolutionized quantum science and atomic physics. They are essential to quantum simulation and sensing, for example underlying atom interferometers in space and ambitious tests of Einstein's equivalence principle. The key to dramatically increasing the bandwidth and precision of such matter-wave sensors lies in sustaining a coherent matter wave indefinitely. Here we demonstrate continuous Bose-Einstein condensation by creating a continuous-wave (CW) condensate of strontium atoms that lasts indefinitely. The coherent matter wave is sustained by amplification through Bose-stimulated gain of atoms from a thermal bath. By steadily replenishing this bath while achieving 1000x higher phase-space densities than previous works, we maintain the conditions for condensation. This advance overcomes a fundamental limitation of all atomic quantum gas experiments to date: the need to execute several cooling stages time-sequentially. Continuous matter-wave amplification will make possible CW atom lasers, atomic counterparts of CW optical lasers that have become ubiquitous in technology and society. The coherence of such atom lasers will no longer be fundamentally limited by the atom number in a BEC and can ultimately reach the standard quantum limit. Our development provides a new, hitherto missing piece of atom optics, enabling the construction of continuous coherent matter-wave devices. From infrasound gravitational wave detectors to optical clocks, the dramatic improvement in coherence, bandwidth and precision now within reach will be decisive in the creation of a new class of quantum sensors.

cond-mat.quant-gas↗

arXiv2021

A steady-state magneto-optical trap of fermionic strontium on a narrow-line transition

A steady-state magneto-optical trap (MOT) of fermionic strontium atoms operating on the 7.5 kHz-wide ${^1\mathrm{S}_0} - {^3\mathrm{P}_1}$ transition is demonstrated. This MOT features $8.4 \times 10^{7}$ atoms, a loading rate of $1.3\times 10^{7}$atoms/s, and an average temperature of 12 $μ$K. These parameters make it well suited to serve as a source of atoms for continuous-wave superradiant lasers operating on strontium's mHz-wide clock transition. Such lasers have only been demonstrated using pulsed Sr sources, limiting their range of applications. Our MOT makes an important step toward continuous operation of these devices, paving the way for continuous-wave active optical clocks.

physics.atom-ph↗

arXiv2019

Continuous guided strontium beam with high phase-space density

A continuous guided atomic beam of $^{88}\mathrm{Sr}$ with a phase-space density exceeding $10^{-4}$ in the moving frame and a flux of $3 \times 10^{7} \, \mathrm{at \, s^{-1}}$ is demonstrated. This phase-space density is around three orders of magnitude higher than previously reported for steady-state atomic beams. We detail the architecture necessary to produce this ultracold atom source and characterize its output after $\sim 4 \, \mathrm{cm}$ of propagation. With radial temperatures of less than $1 \,μ\mathrm{K}$ and a velocity of $8.4 \, \mathrm{cm \, s^{-1}}$ this source is ideal for a range of applications. For example, it could be used to replenish the gain medium of an active optical superradiant clock or be employed to overcome the Dick effect that can limit the performance of pulsed-mode atom interferometers, atomic clocks and ultracold atom based sensors in general. Finally, this result represents a significant step towards the development of a steady-state atom laser.

physics.atom-ph↗

arXiv2018

Sisyphus Optical Lattice Decelerator

We experimentally demonstrate a variation on a Sisyphus cooling technique that was proposed for cooling antihydrogen. In our implementation, atoms are selectively excited to an electronic state whose energy is spatially modulated by an optical lattice, and the ensuing spontaneous decay completes one Sisyphus cooling cycle. We characterize the cooling efficiency of this technique on a continuous beam of Sr, and compare it with radiation pressure based laser cooling. We demonstrate that this technique provides similar atom number for lower end temperatures, provides additional cooling per scattering event and is compatible with other laser cooling methods. This method can be instrumental in bringing new exotic species and molecules to the ultracold regime.

physics.atom-ph↗