Monika H. Schleier-Smith, Ian D. Leroux, Vladan Vuletić
Nov 19, 2009·quant-ph·PDF We propose and analyze a simple method to squeeze dynamically and unconditionally the collective spin of a dilute atomic ensemble by interaction with a driven mode of an optical resonator, as recently demonstrated [I. D. L., M. H. S., and V. V., Phys. Rev. Lett. 104, 073602 (2010)]. We show that substantial squeezing can be achieved in the regime of strong collective ensemble-resonator coupling. The squeezing is ultimately limited either by photon emission into free space or by the curvature of the Bloch sphere. We derive both limits and show where each prevails.
Chi Shu, Simone Colombo, Zeyang Li, Albert Adiyatullin, Enrique Mendez, Edwin Pedrozo-Peñafiel, Vladan Vuletić
The strong coupling of atoms to optical cavities can improve optical lattice clocks as the cavity enables metrologically useful collective atomic entanglement and high-fidelity measurement. To this end, it is necessary to cool the ensemble to suppress motional broadening, and advantageous to maximize and homogenize the atom-cavity coupling. We demonstrate resolved Raman sideband cooling via the cavity as a method that can simultaneously achieve both goals. In 200 ms, we cool 171Yb atoms to an average vibration number <nx> = 0.23(7) in the tightly binding direction, resulting in 93% optical π-pulse fidelity on the clock transition 1S0 -> 3P0. During cooling, the atoms self-organize into locations with maximal atom-cavity-coupling, which will improve quantum metrology applications.
Haruka Tanji, Saikat Ghosh, Jonathan Simon, Benjamin Bloom, Vladan Vuletić
Aug 27, 2008·quant-ph·PDF We demonstrate a heralded quantum memory based on mapping of a photon polarization state onto a single collective-spin excitation (magnon) shared between two spatially overlapped atomic ensembles. The polarization fidelity is measured by quantum state tomography to be above 90(2)% for any input polarization, which far exceeds the classical limit of 2/3. The process also constitutes a quantum non-destructive probe that detects and regenerates a photon without touching its - potentially undetermined - polarization.
Zachary Vendeiro, Joshua Ramette, Alyssa Rudelis, Michelle Chong, Josiah Sinclair, Luke Stewart, Alban Urvoy, Vladan Vuletić
Machine learning is emerging as a technology that can enhance physics experiment execution and data analysis. Here, we apply machine learning to accelerate the production of a Bose-Einstein condensate (BEC) of $^{87}\mathrm{Rb}$ atoms by Bayesian optimization of up to 55 control parameters. This approach enables us to prepare BECs of $2.8 \times 10^3$ optically trapped $^{87}\mathrm{Rb}$ atoms from a room-temperature gas in 575 ms. The algorithm achieves the fast BEC preparation by applying highly efficient Raman cooling to near quantum degeneracy, followed by a brief final evaporation. We anticipate that many other physics experiments with complex nonlinear system dynamics can be significantly enhanced by a similar machine-learning approach.
Emanuele G. Dalla Torre, Johannes Otterbach, Eugene Demler, Vladan Vuletic, Mikhail D. Lukin
Sep 10, 2012·quant-ph·PDF We present and analyze a new approach for the generation of atomic spin squeezed states. Our method involves the collective coupling of an atomic ensemble to a decaying mode of an open optical cavity. We demonstrate the existence of a collective atomic dark-state, decoupled from the radiation field. By explicitly constructing this state we find that it can feature spin squeezing bounded only by the Heisenberg limit. We show that such dark states can be deterministically prepared via dissipative means, thus turning dissipation into a resource for entanglement. The scaling of the phase sensitivity taking realistic imperfections into account is discussed.
Leon Karpa, Alexei Bylinskii, Dorian Gangloff, Marko Cetina, Vladan Vuletić
We report the localization of an ion by a one-dimensional optical lattice in the presence of an applied external force. The ion is confined radially by a radiofrequency trap and axially by a combined electrostatic and optical-lattice potential. The ion is cooled using a resolved Raman sideband technique to a mean vibrational number <n> = 0.6 \pm 0.1 along the optical lattice. We implement a detection method to monitor the position of the ion subject to a periodic electrical driving force with a resolution down to λ/40, and demonstrate suppression of the driven ion motion and localization to a single lattice site on time scales of up to 10 milliseconds. This opens new possibilities for studying many-body systems with long-range interactions in periodic potentials.
Dorian A. Gangloff, Alexei Bylinskii, Vladan Vuletić
The frictional dynamics of interacting surfaces under forced translation are critically dependent on lattice commensurability. Performing experiments in a trapped-ion friction emulator, we observe two distinct structural and frictional phases: a commensurate high-friction phase where the ions stick-slip simultaneously over the lattice, and an incommensurate low-friction phase where the propagation of a kink breaks that simultaneity. We experimentally track the kink's propagation with atom-by-atom and sub-lattice site resolution, and show that its velocity increases with commensurability. Our results elucidate the commensurate-incommensurate transition and the connection between the appearance of kinks and the reduction of friction in a finite system, with important consequences for controlling friction at nanocontacts.
Yiheng Duan, Mahdi Hosseini, Kristin M. Beck, Vladan Vuletić
Sep 27, 2019·quant-ph·PDF Quantum mechanical expectation values for subsets can differ substantially from those for the whole ensemble. This implies that the effect of interactions between two systems can be altered substantially by conditioning. Here we experimentally demonstrate that, for two light fields $ψ_S$ (signal) and $ψ_A$ (ancilla) that have only weakly interacted with one another, subsequent measurements on the ancilla can produce substantial conditional amplification, attenuation, or phase shift of $ψ_S$. We observe conditional signal power changes within a factor of 30, and phase shift up to $π/2$, induced by small changes in the ancilla measurement basis. The method is generically applicable to a variety of systems, and allows one to modify or boost a given interaction by trading in success probability for interaction strength.
Akio Kawasaki, Boris Braverman, Edwin Pedrozo-Peñafiel, Chi Shu, Simone Colombo, Zeyang Li, Özge Özel, Wenlan Chen, Leonardo Salvi, André Heinz, David Levonian, Daisuke Akamatsu, Yanhong Xiao, Vladan Vuletić
Optical cavities are widely used to enhance the interaction between atoms and light. Typical designs using a geometrically symmetric structure in the near-concentric regime face a tradeoff between mechanical stability and high single-atom cooperativity. To overcome this limitation, we design and implement a geometrically asymmetric standing-wave cavity. This structure, with mirrors of very different radii of curvature, allows strong atom-light coupling while exhibiting good stability against misalignment. We observe effective cooperativities ranging from $η_{\rm eff}=10$ to $η_{\rm eff}=0.2$ by shifting the location of the atoms in the cavity mode. By loading $^{171}$Yb atoms directly from a mirror magneto-optical trap into a one-dimensional optical lattice along the cavity mode, we produce atomic ensembles with collective cooperativities up to $Nη=2\times 10^4$. This system opens a way to preparing spin squeezing for an optical lattice clock and to accessing a range of nonclassical collective states.
Pietro Maria Bonetti, Andrea Rucci, Vladan Vuletic, Maria Luisa Chiofalo
The Aubry transition between sliding and pinned phases, driven by the competition between two incommensurate length scales, represents a paradigm that is applicable to a large variety of microscopically distinct systems. Despite previous theoretical studies, it remains an open question to what extent quantum effects modify the transition, or are experimentally observable. An experimental platform that can potentially reach the quantum regime has recently become available in the form of trapped laser-cooled ions subject to a periodic optical potential [A. Bylinskii, D. Gangloff, I. Counts, and V. Vuletic, Nature Materials 15, 717 (2016)]. Using Path-Integral Monte Carlo (PIMC) simulation methods, we analyze the impact of quantum tunneling on the sliding-to-pinned transition in this system, and determine the phase diagram in terms of incommensuration and potential strength. We propose new signatures of the quantum Aubry transition that are robust against thermal and finite-size effects, and that can be observed in future experiments.
Dolev Bluvstein, Ahmed Omran, Harry Levine, Alexander Keesling, Giulia Semeghini, Sepehr Ebadi, Tout T. Wang, Alexios A. Michailidis, Nishad Maskara, Wen Wei Ho, Soonwon Choi, Maksym Serbyn, Markus Greiner, Vladan Vuletic, Mikhail D. Lukin
Dec 22, 2020·quant-ph·PDF Controlling non-equilibrium quantum dynamics in many-body systems is an outstanding challenge as interactions typically lead to thermalization and a chaotic spreading throughout Hilbert space. We experimentally investigate non-equilibrium dynamics following rapid quenches in a many-body system composed of 3 to 200 strongly interacting qubits in one and two spatial dimensions. Using a programmable quantum simulator based on Rydberg atom arrays, we probe coherent revivals corresponding to quantum many-body scars. Remarkably, we discover that scar revivals can be stabilized by periodic driving, which generates a robust subharmonic response akin to discrete time-crystalline order. We map Hilbert space dynamics, geometry dependence, phase diagrams, and system-size dependence of this emergent phenomenon, demonstrating novel ways to steer entanglement dynamics in many-body systems and enabling potential applications in quantum information science.
Wenchao Xu, Aditya V. Venkatramani, Sergio H. Cantú, Tamara Šumarac, Valentin Klüsener, Mikhail D. Lukin, Vladan Vuletić
May 24, 2021·quant-ph·PDF We demonstrate a new approach for fast preparation, manipulation, and collective readout of an atomic Rydberg-state qubit. By making use of Rydberg blockade inside a small atomic ensemble, we prepare a single qubit within 3~$μ$s with a success probability of $F_p=0.93 \pm 0.02$, rotate it, and read out its state in $6$ $μs$ with a single-shot fidelity of $F_d=0.92 \pm 0.04$. The ensemble-assisted detection is $10^3$ times faster than imaging of a single atom with the same optical resolution, and enables fast repeated non-destructive measurement. We observe qubit coherence times of 15~$μ$s, much longer than the $π$ rotation time of 90~ns. Potential applications ranging from faster quantum information processing in atom arrays to efficient implementation of quantum error correction are discussed.
Uroš Delić, Manuel Reisenbauer, Kahan Dare, David Grass, Vladan Vuletić, Nikolai Kiesel, Markus Aspelmeyer
Nov 11, 2019·quant-ph·PDF We report quantum ground state cooling of a levitated nanoparticle in a room temperature environment. Using coherent scattering into an optical cavity we cool the center of mass motion of a $143$ nm diameter silica particle by more than $7$ orders of magnitude to $n_x=0.43\pm0.03$ phonons along the cavity axis, corresponding to a temperature of $12~μ$K. We infer a heating rate of $Γ_x/2π= 21\pm 3$ kHz, which results in a coherence time of $7.6~μ$s -- or $15$ coherent oscillations -- while the particle is optically trapped at a pressure of $10^{-6}$ mbar. The inferred optomechanical coupling rate of $g_x/2π= 71$ kHz places the system well into the regime of strong cooperativity ($C \approx 5$). We expect that a combination of ultra-high vacuum with free-fall dynamics will allow to further expand the spatio-temporal coherence of such nanoparticles by several orders of magnitude, thereby opening up new opportunities for macrosopic quantum experiments.
Zeyang Li, Boris Braverman, Simone Colombo, Chi Shu, Akio Kawasaki, Albert Adiyatullin, Edwin Pedrozo-Peñafiel, Enrique Mendez, Vladan Vuletić
Jun 22, 2021·quant-ph·PDF The interaction between an atomic ensemble and a light mode in a high-finesse optical cavity can easily reach the strong-coupling regime, where quantum effects dominate. In this regime, the interaction can be used to generate both atom-light and atom-atom entanglement. We analyze the dominant effects on the collective atomic state and the light field, and derive a unified approach that can account for atomic entanglement induced both by measurements on the light field, and by ignoring the state of the light field altogether. We present analytical expressions for the entanglement induced by the interaction, and determine the conditions that maximize the entanglement-induced gain over the standard quantum limit in quantum sensors and atomic clocks.
Ian Counts, Joonseok Hur, Diana P. L. Aude Craik, Honggi Jeon, Calvin Leung, Julian Berengut, Amy Geddes, Akio Kawasaki, Wonho Jhe, Vladan Vuletić
We measure isotope shifts for five Yb$^+$ isotopes with zero nuclear spin on two narrow optical quadrupole transitions ${}^2S_{1/2} \rightarrow {}^2D_{3/2}$, ${}^2S_{1/2} \rightarrow {}^2D_{5/2}$ with an accuracy of $\sim 300$ Hz. The corresponding King plot shows a $3 \times 10^{-7}$ deviation from linearity at the 3 $σ$ uncertainty level. Such a nonlinearity can indicate physics beyond the Standard Model (SM) in the form of a new bosonic force carrier, or arise from higher-order nuclear effects within the SM. We identify the quadratic field shift as a possible contributor to the nonlinearity at the observed scale, and show how the nonlinearity pattern can be used in future, more accurate measurements to separate a new-boson signal from nuclear effects.
Wenlan Chen, Kristin M. Beck, Robert Bücker, Michael Gullans, Mikhail D. Lukin, Haruka Tanji-Suzuki, Vladan Vuletić
Jan 14, 2014·quant-ph·PDF The realization of an all-optical transistor where one 'gate' photon controls a 'source' light beam, is a long-standing goal in optics. By stopping a light pulse in an atomic ensemble contained inside an optical resonator, we realize a device in which one stored gate photon controls the resonator transmission of subsequently applied source photons. A weak gate pulse induces bimodal transmission distribution, corresponding to zero and one gate photons. One stored gate photon produces fivefold source attenuation, and can be retrieved from the atomic ensemble after switching more than one source photon. Without retrieval, one stored gate photon can switch several hundred source photons. With improved storage and retrieval efficiency, our work may enable various new applications, including photonic quantum gates, and deterministic multiphoton entanglement.
Leonardo Salvi, Nicola Poli, Vladan Vuletic, Guglielmo M. Tino
We propose and analyse a method that allows for the production of squeezed states of the atomic center-of-mass motion that can be injected into an atom interferometer. Our scheme employs dispersive probing in a ring resonator on a narrow transition of strontium atoms in order to provide a collective measurement of the relative population of two momentum states. We show that this method is applicable to a Bragg diffraction-based atom interferometer with large diffraction orders. The applicability of this technique can be extended also to small diffraction orders and large atom numbers by inducing atomic transparency at the frequency of the probe field, reaching an interferometer phase resolution scaling $Δφ\sim N^{-3/4}$, where $N$ is the atom number. We show that for realistic parameters it is possible to obtain a 20 dB gain in interferometer phase estimation compared to the Standard Quantum Limit.
Marko Cetina, Andrew Grier, Jonathan Campbell, Isaac Chuang, Vladan Vuletic
We produce large numbers of low-energy ions by photoionization of laser-cooled atoms inside a surface-electrode-based Paul trap. The isotope-selective trap loading rate of $4\times10^{5}$ Yb$^{+}$ ions/s exceeds that attained by photoionization (electron impact ionization) of an atomic beam by four (six) orders of magnitude. Traps as shallow as 0.13 eV are easily loaded with this technique. The ions are confined in the same spatial region as the laser-cooled atoms, which will allow the experimental investigation of interactions between cold ions and cold atoms or Bose-Einstein condensates.
Jiazhong Hu, Zachary Vendeiro, Wenlan Chen, Hao Zhang, Robert McConnell, Anders S. Sørensen, Vladan Vuletić
Jun 17, 2016·quant-ph·PDF We experimentally demonstrate the strictly nonclassical behavior in a many-atom system using a recently derived criterion [E. Kot et al., Phys. Rev. Lett. 108, 233601 (2012)] that explicitly does not make use of quantum mechanics. We thereby show that the magnetic moment distribution measured by McConnell et al. [R. McConnell et al., Nature 519, 439 (2015)] in a system with a total mass of $2.6\times 10^5$ atomic mass units is inconsistent with classical physics. Notably, the strictly nonclassical behavior affects an area in phase space $10^3$ times larger than the Planck quantum $\hbar$.
Jiazhong Hu, Alban Urvoy, Zachary Vendeiro, Valentin Crépel, Wenlan Chen, Vladan Vuletić
We demonstrate direct laser cooling of a gas of rubidium 87 atoms to quantum degeneracy. The method does not involve evaporative cooling, is fast, and induces little atom loss. The atoms are trapped in a two-dimensional optical lattice that enables cycles of cloud compression to increase the density, followed by degenerate Raman sideband cooling to decrease the temperature. Light-induced loss at high atomic density is substantially reduced by using far red detuned optical pumping light. Starting with 2000 atoms, we prepare 1400 atoms in 300 ms at quantum degeneracy, as confirmed by the appearance of a bimodal velocity distribution as the system crosses over from a classical gas to a Bose-condensed, interacting one-dimensional gas with a macroscopic population of the quantum ground state. The method should be broadly applicable to many bosonic and fermionic species, and to systems where evaporative cooling is not possible.