Nuclear singlet state in diamond for overcoming the standard quantum limit in gravitational wave detectors

Project Information

SingletSQL

Grant agreement ID: 101065991

DOI

10.3030/101065991

Project closed

EC signature date 20 June 2022

Start date 15 January 2023

End date 14 January 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 175 920,00

Coordinated by

INTERUNIVERSITAIR MICRO-ELECTRONICA CENTRUM
Belgium

Periodic Reporting for period 1 - SingletSQL (Nuclear singlet state in diamond for overcoming the standard quantum limit in gravitational wave detectors)

Reporting period: 2023-01-15 to 2025-01-14

Summary of the context and overall objectives of the project

O1: As I explained in the proposal, the BAE measurement using an atomic ensemble has a fundamental problem with matching the spin and mechanical oscillator frequencies. Besides, the performance of the scheme is poor at lower frequencies due to a mismatch of susceptibilities. To overcome this problem, I came out with an outstanding solution of a novel scheme how to obtain quantum back action evading measurements performed on an opto-mechanical cavity, which abolishes the necessity of the auxiliary spin system [1].

O2: Squeezing optimization on an optomechanical system is not complete without studying entanglement issues between the parts of the system. Working in this direction, I studied entanglement between optics and mechanics when it is parametrically driven and how the squeezing is being manipulated based on entanglement [2].

O3: I investigated the entanglement and non-locality between specific spectral components of continuous variable two-mode squeezed mixed states, identifying their limits [3,4]. These spectral components are selected from output modes using filters commonly employed in optomechanical systems. I have chosen two different types of filters and determined both thermalization dynamics and steady-state behaviors of the impact of filters.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

WP1: I introduced a double cavity sharing a common mechanical oscillator system where negative radiation pressure coupling between the cavity field and the end mirror is observed [1]. The measurement is performed by sending a two-mode squeezed vacuum to both cavities and detecting the output through heterodyne detection. Compared to the previously proposed schemes, I show that our scheme is capable of suppressing both the quantum noises with more
efficiency. It suppresses shot noise in the same amount and back action noise more efficiently that acts in lower frequencies (<100 Hz), which is more interesting to the community. In addition, the scheme has also proven to be beneficial for reducing thermal noise by a significant amount. The scheme consists of introducing a double cavity with end mirrors interlocked by a pivot and moving in opposite directions.

WP2: I show how to squeeze mechanical motion and entangle the optical field with mechanical motion in an optomechanical system containing a parametric amplification [2]. The scheme is based on optical bistability which emerges in the system for a strong enough driving field. When the steady
state is on the upper branch of the bistable shape, both squeezing and entanglement are greatly enhanced. Regarding the mechanical squeezing, it reaches the standard quantum limit (SQL) in the upper branch of the bistability. Our proposal provides a way to improve quantum effects in optomechanical systems by taking advantage of nonlinearities.

WP3: While studying the impact of filters on the two-mode hybrid squeezing, we consider both the distinct thermalization scenarios, i.e. one occurring in the vacuum state before entering the nonlinear crystal for squeezing and another after the generation of the two-mode squeezed vacuum but before passing through filters and detectors [3,4]. Both entanglement and nonlocality reach their peak when the filters are identical. However, increasing the degree of input squeezing while applying non-identical filters disrupts both entanglement and non-locality, leading to a bell-shaped pattern. Additionally, I provided precise boundaries for entanglement and non-locality. Combined with the filter, the population of two-mode squeezed thermal light influences the angle of a maximally squeezed hybrid quadrature.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Quantum noise is the major issue in the next-generation gravitational wave detector, after the successful suppression of mechanical, electrical, and seismic noises. Developing schemes to suppress it, especially at the lower frequencies is the best possible contribution in this field. My effort, throughout the journey under MSCA, has been able to serve this interest [1]. The follow-up work will be continued by IRI (International Research Infrastructure) which is going to be funded by FWO. Apart from GW physics, the investigation of the entanglement and nonlocality between filtered two-mode squeezed systems has huge applications in the field of quantum information processing and quantum communication [3,4].