RESUMEN
The Rydberg blockade is a key ingredient for entangling atoms in arrays. However, it requires atoms to be spaced well within the blockade radius, which limits the range of local quantum gates. Here we break this constraint using Floquet frequency modulation, with which we demonstrate Rydberg-blockade entanglement beyond the traditional blockade radius and show how the enlarged entanglement range improves qubit connectivity in a neutral atom array. Further, we find that the coherence of entangled states can be extended under Floquet frequency modulation. Finally, we realize Rydberg anti-blockade states for two sodium Rydberg atoms within the blockade radius. Such Rydberg anti-blockade states for atoms at close range enables the robust preparation of strongly-interacting, long-lived Rydberg states, yet their steady-state population cannot be achieved with only the conventional static drive. Our work transforms between the paradigmatic regimes of Rydberg blockade versus anti-blockade and paves the way for realizing more connected, coherent, and tunable neutral atom quantum processors with a single approach.
RESUMEN
Yang-Lee edge singularities (YLES) are the edges of the partition function zeros of an interacting spin model in the space of complex control parameters. They play an important role in understanding non-Hermitian phase transitions in many-body physics, as well as characterizing the corresponding nonunitary criticality. Even though such partition function zeroes have been measured in dynamical experiments where time acts as the imaginary control field, experimentally demonstrating such YLES criticality with a physical imaginary field has remained elusive due to the difficulty of physically realizing non-Hermitian many-body models. We provide a protocol for observing the YLES by detecting kinked dynamical magnetization responses due to broken PT symmetry, thus enabling the physical probing of nonunitary phase transitions in nonequilibrium settings. In particular, scaling analyses based on our nonunitary time evolution circuit with matrix product states accurately recover the exponents uniquely associated with the corresponding nonunitary CFT. We provide an explicit proposal for observing YLES criticality in Floquet quenched Rydberg atomic arrays with laser-induced loss, which paves the way towards a universal platform for simulating non-Hermitian many-body dynamical phenomena.
RESUMEN
We demonstrate microwave dressing on ultracold, fermionic ^{23}Na^{40}K ground-state molecules and observe resonant dipolar collisions with cross sections exceeding 3 times the s-wave unitarity limit. The origin of these interactions is the resonant alignment of the approaching molecules' dipoles along the intermolecular axis, which leads to strong attraction. We explain our observations with a conceptually simple two-state picture based on the Condon approximation. Furthermore, we perform coupled-channel calculations that agree well with the experimentally observed collision rates. The resonant microwave-induced collisions found here enable controlled, strong interactions between molecules, of immediate use for experiments in optical lattices.
RESUMEN
A strong nonlinear coupling between harmonic oscillators is highly desirable for quantum information processing and quantum simulation, but is difficult to achieve in many physical systems. Here, we exploit the Coulomb interaction between two trapped ions to achieve strong nonlinear coupling between normal modes of motion at the single-phonon level. We experimentally demonstrate phonon up- and down-conversion and apply this coupling to directly measure the parity and Wigner functions of the ions' motional states. Our results represent the fully quantum operation of a degenerate parametric oscillator and hold promise for quantum computation schemes that involve continuous variables.
RESUMEN
Coherence, the stability of the relative phase between quantum states, is central to quantum mechanics and its applications. For ultracold dipolar molecules at sub-microkelvin temperatures, internal states with robust coherence are predicted to offer rich prospects for quantum many-body physics and quantum information processing. We report the observation of stable coherence between nuclear spin states of ultracold fermionic sodium-potassium (NaK) molecules in the singlet rovibrational ground state. Ramsey spectroscopy reveals coherence times on the scale of 1 second; this enables high-resolution spectroscopy of the molecular gas. Collisional shifts are shown to be absent down to the 100-millihertz level. This work opens the door to the use of molecules as a versatile quantum memory and for precision measurements on dipolar quantum matter.
RESUMEN
We demonstrate coherent microwave control of rotational and hyperfine states of trapped, ultracold, and chemically stable ^{23}Na^{40}K molecules. Starting with all molecules in the absolute rovibrational and hyperfine ground state, we study rotational transitions in combined magnetic and electric fields and explain the rich hyperfine structure. Following the transfer of the entire molecular ensemble into a single hyperfine level of the first rotationally excited state, J=1, we observe lifetimes of more than 3 s, comparable to those in the rovibrational ground state, J=0. Long-lived ensembles and full quantum state control are prerequisites for the use of ultracold molecules in quantum simulation, precision measurements, and quantum information processing.
RESUMEN
We experimentally demonstrate microwave control of the motional state of a trapped ion placed in a state-dependent potential generated by a running optical lattice. Both the optical lattice depth and the running lattice frequency provide tunability of the spin-motion coupling strength. The spin-motional coupling is exploited to demonstrate sideband cooling of a ^{171}Yb^{+} ion to the ground state of motion.
RESUMEN
Autoionization of Rydberg states of HfF, prepared using the optical-optical double resonance technique, holds promise to create HfF(+) in a particular Zeeman level of a rovibronic state for an electron electric dipole moment search. We characterize a vibronic band of Rydberg HfF at 54 cm(-1) above the lowest ionization threshold and directly probe the state of the ions formed from this vibronic band by performing laser-induced fluorescence on the ions. The Rydberg HfF molecules show a propensity to decay into only a few ion rotational states of a given parity and are found to preserve their orientation qualitatively upon autoionization. We show empirically that we can create 30% of the total ion yield in a particular â£J(+), M(+)
RESUMEN
We investigate experimentally the influence of the grating reflectivity, grating resolution, and diode facet antireflection (AR) coating on the intrinsic linewidth of an external-cavity diode laser built with a diffraction grating in a Littrow configuration. Grating lasers at 399, 780, and 852 nm are determined to have typical linewidths between 250 and 600 kHz from measurements of their frequency noise power spectral densities. The linewidths are little affected by the presence of an AR coating on the diode facet but narrow as the grating reflectivity and grating resolution are increased, with the resolution exerting a greater effect. We also use frequency noise measurements to characterize a laser mount with improved mechanical stability.
RESUMEN
We generated narrowband pairs of nearly identical photons at a rate of 5 x 10(4) pairs per second from a laser-cooled atomic ensemble inside an optical cavity. A two-photon interference experiment demonstrated that the photons could be made 90% indistinguishable, a key requirement for quantum information-processing protocols. Used as a conditional single-photon source, the system operated near the fundamental limits on recovery efficiency (57%), Fourier transform-limited bandwidth, and pair-generation-rate-limited suppression of two-photon events (factor of 33 below the Poisson limit). Each photon had a spectral width of 1.1 megahertz, ideal for interacting with atomic ensembles that form the basis of proposed quantum memories and logic.