30 research outputs found
Observation of discrete time-crystalline order in a disordered dipolar many-body system
Understanding quantum dynamics away from equilibrium is an outstanding
challenge in the modern physical sciences. It is well known that
out-of-equilibrium systems can display a rich array of phenomena, ranging from
self-organized synchronization to dynamical phase transitions. More recently,
advances in the controlled manipulation of isolated many-body systems have
enabled detailed studies of non-equilibrium phases in strongly interacting
quantum matter. As a particularly striking example, the interplay of periodic
driving, disorder, and strong interactions has recently been predicted to
result in exotic "time-crystalline" phases, which spontaneously break the
discrete time-translation symmetry of the underlying drive. Here, we report the
experimental observation of such discrete time-crystalline order in a driven,
disordered ensemble of dipolar spin impurities in diamond at
room-temperature. We observe long-lived temporal correlations at integer
multiples of the fundamental driving period, experimentally identify the phase
boundary and find that the temporal order is protected by strong interactions;
this order is remarkably stable against perturbations, even in the presence of
slow thermalization. Our work opens the door to exploring dynamical phases of
matter and controlling interacting, disordered many-body systems.Comment: 6 + 3 pages, 4 figure
Low phase noise diode laser oscillator for 1S-2S spectroscopy in atomic hydrogen
We report on a low-noise diode laser oscillator at 972 nm actively stabilized
to an ultra-stable vibrationally- and thermally compensated reference cavity.
To increase the fraction of laser power in the carrier we designed a 20 cm long
external cavity diode laser with an intra-cavity electro-optical modulator. The
fractional power in the carrier reaches 99.9% which corresponds to a rms phase
noise of in 10\,MHz bandwidth. Using
this oscillator we recorded 1S-2S spectra in atomic hydrogen and have not
observed any significant loss of the excitation efficiency due to phase noise
multiplication in the three consecutive 2-photon processes.Comment: 3 pages, 5 figure
Experimental Determination of Irreversible Entropy Production in out-of-Equilibrium Mesoscopic Quantum Systems
By making use of a recently proposed framework for the inference of thermodynamic irreversibility in bosonic quantum systems, we experimentally measure and characterize the entropy production rates in the non-equilibrium steady state of two different physical systems -- a micro-mechanical resonator and a Bose-Einstein condensate -- each coupled to a high finesse cavity and hence also subject to optical loss. Key features of our setups, such as cooling of the mechanical resonator and signatures of a structural quantum phase transition in the condensate are reflected in the entropy production rates. Our work demonstrates the possibility to explore irreversibility in driven mesoscopic quantum systems and paves the way to a systematic experimental assessment of entropy production beyond the microscopic limit
A Chemical Biology Solution to Problems with Studying Biologically Important but Unstable 9‑O-Acetyl Sialic Acids
9-O-Acetylation
is a common natural modification on sialic acids
(Sias) that terminate many vertebrate glycan chains. This ester group
has striking effects on many biological phenomena, including microbe-host
interactions, complement action, regulation of immune responses, sialidase
action, cellular apoptosis, and tumor immunology. Despite such findings,
9-O-acetyl sialoglycoconjugates have remained largely understudied,
primarily because of marked lability of the 9-O-acetyl group to even
small pH variations and/or the action of mammalian or microbial esterases.
Our current studies involving 9-O-acetylated sialoglycans on glycan
microarrays revealed that even the most careful precautions cannot
ensure complete stability of the 9-O-acetyl group. We now demonstrate
a simple chemical biology solution to many of these problems by substituting
the oxygen atom in the ester with a nitrogen atom, resulting in sialic
acids with a chemically and biologically stable 9-N-acetyl group.
We present an efficient one-pot multienzyme method to synthesize a
sialoglycan containing 9-acetamido-9-deoxy-<i>N</i>-acetylneuraminic
acid (Neu5Ac9NAc) and compare it to the one with naturally occurring
9-<i>O</i>-acetyl-<i>N</i>-acetylneuraminic acid
(Neu5,9Ac<sub>2</sub>). Conformational resemblance of the two molecules
was confirmed by computational molecular dynamics simulations. Microarray
studies showed that the Neu5Ac9NAc-sialoglycan is a ligand for viruses
naturally recognizing Neu5,9Ac<sub>2</sub>, with a similar affinity
but with much improved stability in handling and study. Feeding of
Neu5Ac9NAc or Neu5,9Ac<sub>2</sub> to mammalian cells resulted in
comparable incorporation and surface expression as well as binding
to 9-O-acetyl-Sia-specific viruses. However, cells fed with Neu5Ac9NAc
remained resistant to viral esterases and showed a slower turnover.
This simple approach opens numerous research opportunities that have
heretofore proved intractable