93 research outputs found
Detection and control of individual nuclear spins using a weakly coupled electron spin
We experimentally isolate, characterize and coherently control up to six
individual nuclear spins that are weakly coupled to an electron spin in
diamond. Our method employs multi-pulse sequences on the electron spin that
resonantly amplify the interaction with a selected nuclear spin and at the same
time dynamically suppress decoherence caused by the rest of the spin bath. We
are able to address nuclear spins with interaction strengths that are an order
of magnitude smaller than the electron spin dephasing rate. Our results provide
a route towards tomography with single-nuclear-spin sensitivity and greatly
extend the number of available quantum bits for quantum information processing
in diamond
Measuring mechanical motion with a single spin
We study theoretically the measurement of a mechanical oscillator using a
single two level system as a detector. In a recent experiment, we used a single
electronic spin associated with a nitrogen vacancy center in diamond to probe
the thermal motion of a magnetized cantilever at room temperature {Kolkowitz et
al., Science 335, 1603 (2012)}. Here, we present a detailed analysis of the
sensitivity limits of this technique, as well as the possibility to measure the
zero point motion of the oscillator. Further, we discuss the issue of
measurement backaction in sequential measurements and find that although
backaction heating can occur, it does not prohibit the detection of zero point
motion. Throughout the paper we focus on the experimental implementation of a
nitrogen vacancy center coupled to a magnetic cantilever; however, our results
are applicable to a wide class of spin-oscillator systems. Implications for
preparation of nonclassical states of a mechanical oscillator are also
discussed.Comment: 17 pages, 6 figure
Dynamics of interacting fermions under spin-orbit coupling in an optical lattice clock
Quantum statistics and symmetrization dictate that identical fermions do not interact via s-wave collisions. However, in the presence of spin-orbit coupling (SOC), fermions prepared in identical internal states with distinct momenta become distinguishable. The resulting strongly interacting system can exhibit exotic topological and pairing behaviours, many of which are yet to be observed in condensed matter systems. Ultracold atomic gases offer a promising pathway for simulating these rich phenomena, but until recently have been hindered by heating and losses. Here we enter a new regime of many-body interacting SOC in a fermionic optical lattice clock (OLC), where the long-lived electronic clock states mitigate unwanted dissipation. Using clock spectroscopy, we observe the precession of the collective magnetization and the emergence of spin-locking effects arising from an interplay between p-wave and SOC-induced exchange interactions. The many-body dynamics are well captured by a collective XXZ spin model, which describes a broad class of condensed matter systems ranging from superconductors to quantum magnets. Furthermore, our work will aid in the design of next-generation OLCs by offering a route for avoiding the observed large density shifts caused by SOC-induced exchange interactions
A microfabricated sensor for thin dielectric layers
We describe a sensor for the measurement of thin dielectric layers capable of
operation in a variety of environments. The sensor is obtained by
microfabricating a capacitor with interleaved aluminum fingers, exposed to the
dielectric to be measured. In particular, the device can measure thin layers of
solid frozen from a liquid or gaseous medium. Sensitivity to single atomic
layers is achievable in many configurations and, by utilizing fast, high
sensitivity capacitance read out in a feedback system onto environmental
parameters, coatings of few layers can be dynamically maintained. We discuss
the design, read out and calibration of several versions of the device
optimized in different ways. We specifically dwell on the case in which
atomically thin solid xenon layers are grown and stabilized, in cryogenic
conditions, from a liquid xenon bath
Gravitational wave detection with optical lattice atomic clocks
We propose a space-based gravitational wave (GW) detector consisting of two spatially separated, drag-free satellites sharing ultrastable optical laser light over a single baseline. Each satellite contains an optical lattice atomic clock, which serves as a sensitive, narrowband detector of the local frequency of the shared laser light. A synchronized two-clock comparison between the satellites will be sensitive to the effective Doppler shifts induced by incident GWs at a level competitive with other proposed space-based GW detectors, while providing complementary features. The detected signal is a differential frequency shift of the shared laser light due to the relative velocity of the satellites, and the detection window can be tuned through the control sequence applied to the atoms’ internal states. This scheme enables the detection of GWs from continuous, spectrally narrow sources, such as compact binary inspirals, with frequencies ranging fromPhysic
A physically motivated analytical expression for the temperature dependence of the zero-field splitting of the nitrogen-vacancy center in diamond
The temperature dependence of the zero-field splitting (ZFS) between the
and levels of the nitrogen-vacancy (NV)
center's electronic ground-state spin triplet can be used as a robust nanoscale
thermometer in a broad range of environments. However, despite numerous
measurements of this dependence in different temperature ranges, to our
knowledge no analytical expression has been put forward that captures the
scaling of the ZFS of the NV center across all relevant temperatures. Here we
present a simple, analytical, and physically motivated expression for the
temperature dependence of the NV center's ZFS that matches all experimental
observations, in which the ZFS shifts in proportion to the occupation numbers
of two representative phonon modes. In contrast to prior models our expression
does not diverge outside the regions of fitting. We show that our model
quantitatively matches experimental measurements of the ZFS from 15 to 500 K in
single NV centers in ultra-pure bulk diamond, and we compare our model and
measurements to prior models and experimental data.Comment: Main text: 7 pages, 4 figures, 1 table, 44 references. Supplemental
Material: 12 pages, 5 figures, 2 tables, 23 reference
Manipulating a qubit through the backaction of sequential partial measurements and real-time feedback
Quantum measurements not only extract information from a system but also
alter its state. Although the outcome of the measurement is probabilistic, the
backaction imparted on the measured system is accurately described by quantum
theory. Therefore, quantum measurements can be exploited for manipulating
quantum systems without the need for control fields. We demonstrate
measurement-only state manipulation on a nuclear spin qubit in diamond by
adaptive partial measurements. We implement the partial measurement via tunable
correlation with an electron ancilla qubit and subsequent ancilla readout. We
vary the measurement strength to observe controlled wavefunction collapse and
find post-selected quantum weak values. By combining a novel quantum
non-demolition readout on the ancilla with real-time adaption of the
measurement strength we realize steering of the nuclear spin to a target state
by measurements alone. Besides being of fundamental interest, adaptive
measurements can improve metrology applications and are key to
measurement-based quantum computing.Comment: 6 pages, 4 figure
Quantitative nanoscale vortex-imaging using a cryogenic quantum magnetometer
Microscopic studies of superconductors and their vortices play a pivotal role
in our understanding of the mechanisms underlying superconductivity. Local
measurements of penetration depths or magnetic stray-fields enable access to
fundamental aspects of superconductors such as nanoscale variations of
superfluid densities or the symmetry of their order parameter. However,
experimental tools, which offer quantitative, nanoscale magnetometry and
operate over the large range of temperature and magnetic fields relevant to
address many outstanding questions in superconductivity, are still missing.
Here, we demonstrate quantitative, nanoscale magnetic imaging of Pearl vortices
in the cuprate superconductor YBCO, using a scanning quantum sensor in form of
a single Nitrogen-Vacancy (NV) electronic spin in diamond. The sensor-to-sample
distance of ~10nm we achieve allows us to observe striking deviations from the
prevalent monopole approximation in our vortex stray-field images, while we
find excellent quantitative agreement with Pearl's analytic model. Our
experiments yield a non-invasive and unambiguous determination of the system's
local London penetration depth, and are readily extended to higher temperatures
and magnetic fields. These results demonstrate the potential of quantitative
quantum sensors in benchmarking microscopic models of complex electronic
systems and open the door for further exploration of strongly correlated
electron physics using scanning NV magnetometry.Comment: Main text (5 pages, 4 figures) plus supplementary material (5 pages,
6 figures). Comments welcome. Further information under
http://www.quantum-sensing.c
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