Hybrid quantum systems have the potential of mitigating current challenges in developing a scalable quantum computer. Of particular interest is the hybridization between atomic and superconducting qubits. We demonstrate a novel experimental setup for transferring and trapping ultracold atoms inside a millikelvin cryogenic environment, where interactions between atomic and superconducting qubits can be established, paving the way for hybrid quantum systems. $^{87}\text{Rb}$ atoms are prepared in a conventional magneto-optical trap and transported via a magnetic conveyor belt into a UHV compatible dilution refrigerator with optical access. We store $5\times10^{8}$ atoms with a lifetime of 794 seconds in the vicinity of the millikelvin stage.
Hybrid quantum systems have the potential of mitigating current challenges in developing a scalable quantum computer. Of particular interest is the hybridization between atomic and superconducting qubits. We demonstrate a novel experimental setup for transferring and trapping ultracold atoms inside a millikelvin cryogenic environment, where interactions between atomic and superconducting qubits can be established, paving the way for hybrid quantum systems. 87Rb atoms are prepared in a conventional magneto-optical trap and transported via a magnetic conveyor belt into a UHV compatible dilution refrigerator with optical access. We store 5×108 atoms with a lifetime of 794 seconds in the vicinity of the millikelvin stage.
Hybrid quantum systems have the potential of mitigating current challenges in developing a scalable quantum computer. Of particular interest is the hybridization between atomic and superconducting qubits. We demonstrate an experimental setup for transferring and trapping ultracold atoms inside a millikelvin cryogenic environment, where interactions between atomic and superconducting qubits may be established, paving the way for hybrid quantum systems. We prepare 87Rb atoms in a conventional magneto-optical trap and transport them via a magnetic conveyor belt into a UHV compatible dilution refrigerator with optical access. We store $5\ifmmode\times\else\texttimes\fi{}{10}^{8}$ atoms with a lifetime of 794 s in the vicinity of the millikelvin stage.
Hybrid quantum systems can be formed that combine the strengths of multiple platforms while avoiding the weaknesses. Here we report on progress toward a hybrid quantum system of neutral atom spins coupled to superconducting qubits. We trap laser-cooled rubidium atoms in the evanescent field of an ultrathin optical fiber, which will be suspended a few microns above a superconducting circuit that resonates at the hyperfine frequency of the Rb atoms, allowing magnetic coupling between the atoms and superconductor. As this will be done in a dilution refrigerator environment, the technical demands on the optical fiber is severe. We have developed and optimized a tapered fiber fabrication system, achieving optical transmission in excess of 99.95% , and fibers that can sustain 400 mW of optical power in a UHV environment. We have also optimized tapered fibers that can support higher order optical modes with high transmission (> 97%), which may be useful for different optical potential geometries. We have developed an in-situ tunable high-Q superconducting microwave resonator that can be tuned to within the resonator linewidth of the 6.8 GHz frequency of the Rb hyperfine transition.
A hybrid quantum computing architecture combining quantum processors and quantum memory units allows for exploiting each component's unique properties to enhance the overall performance of the total system. However, superconducting qubits are highly sensitive to magnetic fields, while spin ensembles require finite fields for control, creating a major integration challenge. In this work, we demonstrate the first experimental setup that satisfies these constraints and provides verified qubit stability. Our cryogenic setup comprises two spatially and magnetically decoupled sample volumes inside a single dilution refrigerator: one hosting flux-tunable superconducting qubits and the other a spin ensemble equipped with a superconducting solenoid generating fields up to 50 mT. We show that several layers of Cryophy shielding and an additional superconducting aluminum shield suppress magnetic crosstalk by more than eight orders of magnitude, ensuring stability of the qubit's performance. Moreover, the operation of the solenoid adds minimal thermal load on the relevant stages of the dilution refrigerator. Our results enable scalable hybrid quantum architectures with low-loss integration, marking a key step toward scalable hybrid quantum computing platforms.
During my PhD, I participated in the full setup from scratch of an experiment that aims at cooling down and manipulating two fermionic alkaline atomic species, 6Li and 40K. Our goal is to study ultracold Fermi mixtures with mass imbalance, and to realize a flexible quantum analog simulator. In fact, for certain quantum many-body problems, such as high critical temperature superconductivity and frustrated anti-ferromagnetism, there is neither complete analytical nor numerical solution. Therefore, cold atoms systems, due to their purity and their high degree of tunability, even on their interaction itself, offer an interesting complementary point of view in the study of those phenomena. As far as the experimental setup is concerned, we built an ultra-high vacuum system, a complete and stable laser source for each species, as well as two performing atomic sources, a 6Li Zeeman slower and a 40K bidimensionnal magneto-optical trap; most of the optical and electrical quantities, as well as the imaging diagnostics, being computer controlled. Once those preliminary steps have been performed and optimized, we could obtain an efficient double magneto-optical trap, containing typically 5x10^9 atoms of 6Li and 8x10^9 atoms of 40K. In this configuration, we produced the first 6Li40K* heteronuclear molecules by photoassociation, for which we identified 70 rovibrational lines. In a second part, I describe in detail the magnetic transport of the atomic mixture, between the magneto-optical trap chamber and a science cell, located in an ultra-high vacuum region with large optical access. The complete setup, from its design to its experimental implementation and optimization, as well as the development of the program and the useful numerical diagnostics, are the heart of my work. The transport efficiency could be tested and optimized, allowing for an efficient transfer of the mixture in the science cell. Thus, after this thesis, all the experimental tools are operational in order to allow for evaporative cooling of the mixture in an optically plugged magnetic trap. Therefore, the field is open for quantum simulation and understanding of many-body problems in ultracold Fermi mixtures.
Hybrid quantum systems provide a promising route toward combining the complementary strengths of distinct physical platforms for quantum information processing. In this context, highly excited Rydberg atoms are particularly attractive due to their strong electric dipole moments, long lifetimes, and compatibility with both optical and microwave frequency regimes. Mechanical resonators, on the other hand, offer long coherence times and the ability to store quantum information in macroscopic degrees of freedom. In this thesis, the development of a novel hybrid platform interfacing ultracold Rydberg atoms with high-overtone bulk acoustic wave resonators (HBARs) in a cryogenic environment is presented. The core components of the experimental apparatus have been designed, assembled, and characterized, including a room-temperature realization featuring the complete cold-atom preparation chain. A first-generation superconducting atom chip for trapping ultracold atoms in a cryogenic environment has been designed and fabricated, establishing the foundation for future experiments under cryogenic conditions. The full experimental realization of the hybrid system, including the integration of the mechanical resonator, was delayed by the delivery of a custom-built cryostat. Nevertheless, the preparation of the cryogenic experiment has been completed, enabling rapid progress toward first experiments once cryogenic operation becomes available. At an operating temperature of 4 K, thermal phonon occupation of HBAR modes is significantly reduced compared to room temperature but remains above the quantum ground state, motivating the development of active cooling strategies. Complementing the experimental work, the feasibility of cooling a mechanical mode toward its quantum mechanical ground state using a cloud of Rydberg atoms is investigated theoretically. In this approach, Rydberg atoms act as a dissipative resource that extracts phononic excitations from the mechanical resonator and removes them via radiative decay. Furthermore, the potential of Rydberg atom-mediated interactions to generate entanglement between spatially separated mechanical oscillators is analyzed. Together, these results establish a foundation for future experimental investigations of Rydberg atom–mechanical oscillator hybrid systems.
Current superconducting quantum computers (QC) rely on a brute-force scaling approach where quantum chips operating at the millikelvin stage inside dilution refrigerators are connected to room-temperature electronics via an ever-increasing number of signal wires. In order to drastically scale up such systems without facing refrigeration challenges, these quantum interface electronics need to be integrated at cryogenic temperatures, ideally at the same stage as qubits. In this paper, we show that, by employing energy-efficient digital superconducting microchips based on single flux quantum (SFQ) technology, all essential functions to operate a full stack quantum computer can be integrated at 10 mK. They include digital qubit charge control and magnetic flux control for single- and two-qubit gates, as well as digital qubit readout.