ForschungTopical Groups
Sub-standard quantum limit in suspended interferometers

Sub-standard quantum limit in suspended interferometers


This topical group operates a 10-metre prototype interferometer facility located in the institute for gravitational physics. The 10-m prototype offers an environment with extremely low displacement noise, a large volume in ultra-high vacuum, a highly stable laser with a power of 35 watts, a very stable DC supply network, comprehensive detection of environmental influences, fully digital control infrastructure and sufficient flexibility to quickly change the experimental setup - if necessary.

The first and most important experiment being set up in this facility is a Michelson interferometer, which explores the interferometric standard quantum limit (SQL). To achieve the SQL, the interferometer sensitivity must be limited only by the quantum noise at the measurement frequency. The SQL can be surpassed by exploiting correlations between the amplitude and phase quantum fluctuations of the light inside the interferometer. Different approaches for surpassing the SQL will be tested and analysed.


  • low noise mirror suspensions
  • seismic isolation systems (active/passive)
  • low noise actuators
  • precision interferometry
  • shot noise limited photodiodes
  • laser stabilisation (amplitude/frequency)
  • optical scattering of mirrors
  • vacuum out-gassing test chamber
  • microscopical investigation of surfaces
  • in vacuum seismically isolated platforms


Brown DD, Jones P, Rowlinson S, Leavey S, Green AC, Töyrä D et al. PYKAT: Python package for modelling precision optical interferometers. SoftwareX. 2020 Jul 1;12. 100613. doi.org/10.1016/j.softx.2020.100613

Involved QF Members
Members Institution Relevant Expertise
Harald Lück, LeaderAEINext Generation Gravitational Wave Observatories; Sub-Standard Quantum Limit Interferometry
Matteo CarlassaraAEICommissioning of the SQL Interferometer
Michèle HeursAEIBackaction-Evading Techniques
Benno WillkeAEISqueezed Light Sources; Advanced Light Sources
David WuAEISub-Standard Quantum Limit Interferometry
Sean LeaveyAEISub-Standard Quantum Limit Interferometry, electronics
Philip KochAEIoptics, suspensions
Johannes LehmannAEImirror suspensions
Robin KirchhoffAEIseismic isolation
Juliane von WrangelAEIfibre welding, bonding
Janis WöhlerAEIthermal noise interferometer
Henning VahlbruchAEISqueezed states of light
Jian LiuAEISub-Standard Quantum Limit Interferometry
Luise KranzhoffAEIInertial sensors
Sara al KershiAEIMirror suspensions
Alexander HeidtAEIViolin modes