arXiv subjects

T. McRae

Publications and source records attributed to T. McRae.

4 recordsLinked to original sources

arXiv2021

Approaching the motional ground state of a 10 kg object

The motion of a mechanical object -- even a human-sized object -- should be governed by the rules of quantum mechanics. Coaxing them into a quantum state is, however, difficult: the thermal environment masks any quantum signature of the object's motion. Indeed, the thermal environment also masks effects of proposed modifications of quantum mechanics at large mass scales. We prepare the center-of-mass motion of a 10 kg mechanical oscillator in a state with an average phonon occupation of 10.8. The reduction in temperature, from room temperature to 77 nK, is commensurate with an 11 orders-of-magnitude suppression of quantum back-action by feedback -- and a 13 orders-of-magnitude increase in the mass of an object prepared close to its motional ground state. This begets the possibility of probing gravity on massive quantum systems.

quant-ph↗

arXiv2021

LIGOs Quantum Response to Squeezed States

Gravitational Wave interferometers achieve their profound sensitivity by combining a Michelson interferometer with optical cavities, suspended masses, and now, squeezed quantum states of light. These states modify the measurement process of the LIGO, VIRGO and GEO600 interferometers to reduce the quantum noise that masks astrophysical signals; thus, improvements to squeezing are essential to further expand our gravitational view of the universe. Further reducing quantum noise will require both lowering decoherence from losses as well more sophisticated manipulations to counter the quantum back-action from radiation pressure. Both tasks require fully understanding the physical interactions between squeezed light and the many components of km-scale interferometers. To this end, data from both LIGO observatories in observing run three are expressed using frequency-dependent metrics to analyze each detector's quantum response to squeezed states. The response metrics are derived and used to concisely describe physical mechanisms behind squeezing's simultaneous interaction with transverse-mode selective optical cavities and the quantum radiation pressure noise of suspended mirrors. These metrics and related analysis are broadly applicable for cavity-enhanced optomechanics experiments that incorporate external squeezing, and -- for the first time -- give physical descriptions of every feature so far observed in the quantum noise of the LIGO detectors.

physics.ins-det↗

arXiv2020

Neutron Star Extreme Matter Observatory: A kilohertz-band gravitational-wave detector in the global network

Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly-rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2-4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a neutron star extreme matter observatory (NEMO): a gravitational-wave interferometer optimized to study nuclear physics with merging neutron stars. The concept uses high circulating laser power, quantum squeezing and a detector topology specifically designed to achieve the high-frequency sensitivity necessary to probe nuclear matter using gravitational waves. Above one kHz, the proposed strain sensitivity is comparable to full third-generation detectors at a fraction of the cost. Such sensitivity changes expected event rates for detection of post-merger remnants from approximately one per few decades with two A+ detectors to a few per year, and potentially allows for the first gravitational-wave observations of supernovae, isolated neutron stars, and other exotica.

astro-ph.HE↗

arXiv2020

Quantum correlations between the light and kilogram-mass mirrors of LIGO

Measurement of minuscule forces and displacements with ever greater precision encounters a limit imposed by a pillar of quantum mechanics: the Heisenberg uncertainty principle. A limit to the precision with which the position of an object can be measured continuously is known as the standard quantum limit (SQL). When light is used as the probe, the SQL arises from the balance between the uncertainties of photon radiation pressure imposed on the object and of the photon number in the photoelectric detection. The only possibility surpassing the SQL is via correlations within the position/momentum uncertainty of the object and the photon number/phase uncertainty of the light it reflects. Here, we experimentally prove the theoretical prediction that this type of quantum correlation is naturally produced in the Laser Interferometer Gravitational-wave Observatory (LIGO). Our measurements show that the quantum mechanical uncertainties in the phases of the 200 kW laser beams and in the positions of the 40 kg mirrors of the Advanced LIGO detectors yield a joint quantum uncertainty a factor of 1.4 (3dB) below the SQL. We anticipate that quantum correlations will not only improve gravitational wave (GW) observatories but all types of measurements in future.

quant-ph↗