Quantum expander for gravitational-wave observatories

December 10, 2019

Ultra-stable laser light that was stored in optical resonators of up to 4km length enabled the first observations of gravitational waves from inspirals of binary black holes and neutron stars. Due to the rather low bandwidth of the optical resonator system, however, the scientifically highly interesting post-merger signals at frequencies above a few hundred hertz could not be resolved. Such information would give access to the physics of neutron stars, allowing to study the ultra-dense quantum matter and possibly to find the missing link between gravity and quantum physics.

Recently, scientists MSc. Mikhail Korobko and Prof. Roman Schnabel from the University of Hamburg and Dr. Yiqiu Ma and Prof. Yanbei Chen from the California Institute of Technology proposed a novel all-optical approach to expanding the detection bandwidth of gravitational-wave observatories towards kilohertz frequencies.

What they call 'quantum expander' takes advantage of squeezing the quantum uncertainty of the laser light inside the optical resonator system. While squeezing the quantum uncertainty of the laser light before injection into the resonator system is already routinely used in all gravitational-wave observatories since April 2019, the new add-on will specifically improve the signal-to-noise-ratio at kilohertz frequencies, in fact, without deteriorating today's high performance at lower frequencies.

The scientists propose placing a nonlinear crystal inside the so-called signal-recycling cavity, which is a subsystem in every gravitational-wave observatory today and pump this crystal with green laser light having half the wavelength of the main laser light used in the observatory. The interaction between the pump and the main light leads to a squeezed uncertainty in the quantum fluctuations of the main laser. When the signal-recycling cavity length is controlled to remain a non-integer multiple of the laser wavelength, especially the high frequency quantum fluctuations of the laser light are squeezed in addition to any squeezing injected from the outside.

The newly invented 'quantum expander' is fully compatible with previously invented quantum-noise-suppression techniques. It is intrinsically stable and doesn't require significant modifications to the general topology of the observatories. What it does require is a further improved quality of optical components for further reduction in loss of photons. The 'quantum expander' may find applications beyond gravitational-wave detection in the areas of quantum metrology and quantum optomechanics.
Their research results were recently published in Light: Science and Applications.

Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

Related Quantum Articles from Brightsurf:

Theoreticians show which quantum systems are suitable for quantum simulations
A joint research group led by Prof. Jens Eisert of Freie Universit├Ąt Berlin and Helmholtz-Zentrum Berlin (HZB) has shown a way to simulate the quantum physical properties of complex solid state systems.

Quantum shake
There they were, in all their weird quantum glory: ultracold lithium atoms in the optical trap operated by UC Santa Barbara undergraduate student Alec Cao and his colleagues in David Weld's atomic physics group.

New evidence for quantum fluctuations near a quantum critical point in a superconductor
A study has found evidence for quantum fluctuations near a quantum critical point in a superconductor.

Quantum simulation of quantum crystals
International research team describes the new possibilities offered by the use of ultracold dipolar atoms

Quantum machines learn "quantum data"
Skoltech scientists have shown that quantum-enhanced machine learning can be used on quantum (as opposed to classical) data, overcoming a significant slowdown common to these applications and opening a ''fertile ground to develop computational insights into quantum systems''.

Simulating quantum 'time travel' disproves butterfly effect in quantum realm
Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no 'butterfly effect.' In the research, information--qubits, or quantum bits--'time travel' into the simulated past.

Orbital engineering of quantum confinement in high-Al-content AlGaN quantum well
Recently, professor Kang's group focus on the limitation of quantum confine band offset model, the hole states delocalization in high-Al-content AlGaN quantum well are understood in terms of orbital intercoupling.

Quantum classifiers with tailored quantum kernel?
Quantum information scientists have introduced a new method for machine learning classifications in quantum computing.

A Metal-like Quantum Gas: A pathbreaking platform for quantum simulation
Coherent and ultrafast laser excitation creates an exotic matter phase with spatially overlapping electronic wave-functions under nanometric control in an artificial micro-crystal of ultracold atoms.

Quantum leap: Photon discovery is a major step toward at-scale quantum technologies
A team of physicists at the University of Bristol has developed the first integrated photon source with the potential to deliver large-scale quantum photonics.

Read More: Quantum News and Quantum Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.