1,364 research outputs found
Long spin coherence times in the ground state and an optically excited state of Er:YSiO at zero magnetic field
Spins in solids are an ideal candidate to act as a memory and interface with
superconducting qubits due to their long coherence times. We spectroscopically
investigate erbium-167-doped yttrium orthosilicate as a possible
microwave-addressed memory employing its microwave frequency transitions that
occur without applying an external magnetic field. We obtain coherence times of
380 s in a ground state spin transition and 1.48 ms in an excited state
spin transition. This is 28 times longer compared to previous zero field
measurements, as well as 200 times longer than a previous microwave memory
demonstration in the same material. These long coherence times show that
erbium-167-doped yttrium orthosilicate has potential as a microwave-addressed
quantum memory.Comment: 9 pages, 7 figures. The paper has been expanded compared to the
previous version on arXiv, and the title has change
Optically unstable phase from ion-ion interactions in an erbium doped crystal
We demonstrate an optical unstable phase for a laser driven erbium ion
ensemble. The transmitted light through an erbium-doped yttrium orthosillicate
crystal becomes dynamically unstable when illuminated by a strong
continuous-wave laser. Transient net gain was recorded if the light passes the
sample twice. The experimental results are understood in the framework of a
many-body system interacting with a classical field, where the ion-ion
interaction becomes significant as a result of the high erbium concentration. A
Bloch-equation model that includes the excitation-induced frequency-shift is
introduced to discuss the conditions of the instabilities.Comment: 5 pages, 4 figure
Extending Phenomenological Crystal-Field Methods to Point-Group Symmetry: Characterization of the Optically-Excited Hyperfine Structure of Er:YSiO
We show that crystal-field calculations for point-group symmetry are
possible, and that such calculations can be performed with sufficient accuracy
to have substantial utility for rare-earth based quantum information
applications. In particular, we perform crystal-field fitting for a
C-symmetry site in Er:YSiO. The calculation
simultaneously includes site-selective spectroscopic data up to 20,000
cm, rotational Zeeman data, and ground- and excited-state hyperfine
structure determined from high-resolution Raman-heterodyne spectroscopy on the
1.5 m telecom transition. We achieve an agreement of better than 50 MHz
for assigned hyperfine transitions. The success of this analysis opens the
possibility of systematically evaluating the coherence properties, as well as
transition energies and intensities, of any rare-earth ion doped into
YSiO .Comment: 6 pages, plus 5 pages in supplementary information, 4 figures tota
Experimental implementation of precisely tailored light-matter interaction via inverse engineering
Accurate and efficient quantum control in the presence of constraints and decoherence is a requirement and a challenge in quantum information processing. Shortcuts to adiabaticity, originally proposed to speed up the slow adiabatic process, have nowadays become versatile toolboxes for preparing states or controlling the quantum dynamics. Unique shortcut designs are required for each quantum system with intrinsic physical constraints, imperfections, and noise. Here, we implement fast and robust control for the state preparation and state engineering in a rare-earth ions system. Specifically, the interacting pulses are inversely engineered and further optimized with respect to inhomogeneities of the ensemble and the unwanted interaction with other qubits. We demonstrate that our protocols surpass the conventional adiabatic schemes, by reducing the decoherence from the excited-state decay and inhomogeneous broadening. The results presented here are applicable to other noisy intermediate-scale quantum systems.We acknowledge the support from National Natural Science Foundation of China (NSFC) (61505133, 61674112, 62074107); Natural Science Foundation of Jiang Su Province (BK20150308); The International Cooperation and Exchange of the National Natural Science Foundation of China NSFC-STINT (61811530020); S.K. acknowledges the support from the Swedish Research Council (no. 2016-04375, no. 2019-04949), the Knut and Alice Wallenberg Foundation (KAW2016.0081) and Wallenberg Center for Quantum Technology (WACQT) (KAW2017.0449); European Union's Horizon 2020 research and innovation program (712721); NanOQ Tech and the Lund Laser Centre (LLC) through a project grant under the Lund Linneaus environment. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 820391 (SQUARE) and no. 654148 Laserlab-Europe. A.W. acknowledges the support from the Swedish Research Counc[.R. acknowledges the support from the Swedish Research Council (no. 2016-05121). X.C. acknowledges the support by the Spanish Ministry of Science and the European Regional Development Fund through PGC2018-101355-B-I00 (MCIU/AEI/FEDER, UE) and the Basque Government through Grant No. IT986-16, the EU FET Open Grant Quromorphic (Grant No. 828826), and EPIQUS (Grant No. 899368) and the Ramon y Cajal program (Grant No. RYC-2017-22482)
Strong Purcell enhancement of an optical magnetic dipole transition
Engineering the local density of states with nanophotonic structures is a
powerful tool to control light-matter interactions via the Purcell effect. At
optical frequencies, control over the electric field density of states is
typically used to couple to and manipulate electric dipole transitions.
However, it is also possible to engineer the magnetic density of states to
control magnetic dipole transitions. In this work, we experimentally
demonstrate the optical magnetic Purcell effect using a single rare earth ion
coupled to a nanophotonic cavity. We engineer a new single photon emitter,
Er in MgO, where the electric dipole decay rate is strongly suppressed
by the cubic site symmetry, giving rise to a nearly pure magnetic dipole
optical transition. This allows the unambiguous determination of a magnetic
Purcell factor . We further extend this technique to realize a
magnetic dipole spin-photon interface, performing optical spin initialization
and readout of a single Er electron spin. This work demonstrates the
fundamental equivalence of electric and magnetic density of states engineering,
and provides a new tool for controlling light-matter interactions for a broader
class of emitters
Optical coherence properties of Kramers' rare-earth ions at the nanoscale for quantum applications
Rare-earth (RE) ion doped nano-materials are promising candidates for a range
of quantum technology applications. Among RE ions, the so-called Kramers' ions
possess spin transitions in the GHz range at low magnetic fields, which allows
for high-bandwidth multimode quantum storage, fast qubit operations as well as
interfacing with superconducting circuits. They also present relevant optical
transitions in the infrared. In particular, Er has an optical transition
in the telecom band, while Nd presents a high-emission-rate transition
close to 890 nm. In this paper, we measure spectroscopic properties that are of
relevance to using these materials in quantum technology applications. We find
the inhomogeneous linewidth to be 10.7 GHz for Er and 8.2 GHz for
Nd, and the excited state lifetime T to be 13.68 ms for Er
and 540 s for Nd. We study the dependence of homogeneous linewidth
on temperature for both samples, with the narrowest linewidth being 379 kHz
(T = 839 ns) for Er measured at 3 K, and 62 kHz (T = 5.14
s) for Nd measured at 1.6 K. Further, we investigate time-dependent
homogeneous linewidth broadening due to spectral diffusion and the dependence
of homogeneous linewidth on magnetic field, in order to get additional clarity
of mechanisms that can influence the coherence time. In light of our results,
we discuss two applications: single qubit-state readout and a Fourier-limited
single photon source.Comment: 9 pages, 5 figure
Frequency and evolution of sleep-wake disturbances after ischemic stroke: A 2-year prospective study of 437 patients.
OBJECTIVE
In the absence of systematic and longitudinal data, this study prospectively assessed both frequency and evolution of sleep-wake disturbances (SWD) after stroke.
METHODS
In 437 consecutively recruited patients with ischemic stroke or transient ischemic attack (TIA), stroke characteristics and outcome were assessed within the 1st week and 3.2 ± 0.3 years (M±SD) after the acute event. SWD were assessed by interview and questionnaires at 1 and 3 months as well as 1 and 2 years after the acute event. Sleep disordered breathing (SDB) was assessed by respirography in the acute phase and repeated in one fifth of the participants 3 months and 1 year later.
RESULTS
Patients (63.8% male, 87% ischemic stroke and mean age 65.1 ± 13.0 years) presented with mean NIHSS-score of 3.5 ± 4.5 at admission. In the acute phase, respiratory event index was >15/h in 34% and >30/h in 15% of patients. Over the entire observation period, the frequencies of excessive daytime sleepiness (EDS), fatigue and insomnia varied between 10-14%, 22-28% and 20-28%, respectively. Mean insomnia and EDS scores decreased from acute to chronic stroke, whereas restless legs syndrome (RLS) percentages (6-9%) and mean fatigue scores remained similar. Mean self-reported sleep duration was enhanced at acute stroke (month 1: 07:54 ± 01:27h) and decreased at chronic stage (year 2: 07:43 ± 01:20h).
CONCLUSIONS
This study documents a high frequency of SDB, insomnia, fatigue and a prolonged sleep duration after stroke/TIA, which can persist for years. Considering the negative effects of SWD on physical, brain and mental health these data suggest the need for a systematic assessment and management of post-stroke SWD
Pharmacodynamics effects of CDK4/6 inhibitor LEE011 (ribociclib) in high-risk, localised prostate cancer: a study protocol for a randomised controlled phase II trial (LEEP study: LEE011 in high-risk, localised Prostate cancer)
INTRODUCTION: Despite the development of new therapies for advanced prostate cancer, it remains the most common cause of cancer and the second leading cause of cancer death in men. It is critical to develop novel agents for the treatment of prostate cancer, particularly those that target aspects of androgen receptor (AR) signalling or prostate biology other than inhibition of androgen synthesis or AR binding. Neoadjuvant pharmacodynamic studies allow for a rational approach to the decisions regarding which targeted therapies should progress to phase II/III trials. CDK4/6 inhibitors have evidence of efficacy in breast cancer, and have been shown to have activity in preclinical models of hormone sensitive and castrate resistant prostate cancer. The LEEP trial aims to assess the pharmacodynamic effects of LEE011 (ribociclib), an orally bioavailable and highly selective CDK4/6 inhibitor, in men undergoing radical prostatectomy for high-risk, localised prostate cancer. METHODS AND ANALYSIS: The multicentre randomised, controlled 4:1 two-arm, phase II, open label pharmacodynamic study will recruit 47 men with high risk, localised prostate cancer who are planned to undergo radical prostatectomy. Participants who are randomised to receive the study treatment will be treated with LEE011 400 mg daily for 21 days for one cycle. The primary endpoint is the frequency of a 50% reduction in Ki-67 proliferation index from the pretreatment prostate biopsy compared to that present in prostate cancer tissue from radical prostatectomy. Secondary and tertiary endpoints include pharmacodynamic assessment of CDK4/6 cell cycle progression via E2F levels, apoptotic cell death by cleaved caspase-3, changes in serum and tumour levels of Prostate Specific Antigen (PSA), pathological regression, safety via incidence of adverse events and exploratory biomarker analysis. ETHICS AND DISSEMINATION: The protocol was approved by a central ethics review committee (St Vincent's Hospital HREC) for all participating sites (HREC/17/SVH/294). Results will be disseminated in peer-reviewed journals and at scientific conferences. DRUG SUPPLY: Novartis. PROTOCOL VERSION: 2.0, 30 May 2019 TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trials Registry (ACTRN12618000354280).Tahlia Scheinberg, James Kench, Martin Stockler, Kate L Mahon, Lucille Sebastian, Phillip Stricker, Anthony M Joshua, H Woo, Ruban Thanigasalam, Nariman Ahmadi, Margaret M Centenera, Lisa M Butler, Lisa G Horvat
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