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Michèle Heurs Max-Planck-Institut für Gravitationsphysik & QUEST -- Leibniz Universität Hannover
OIST Workshop Okinawa
May 2013
MPI für Gravitationsphysik Albert-Einstein-Institut
Hannover
May 2013 OIST Workshop Okinawa 3
non-classical light sources: squeezed light at high free spectral ranges
controls theory: modern control, coherent control, traditional control
electronics: high-frequency large bandwidth photodetection
precision metrology: stable high-finesse optical resonators, gravitational wave detection
Visit our new website!
http://quantumcontrol.aei.uni-hannover.de/
Gravitational Waves and the interferometric gravitational wave detector network
Standard Quantum Limit of interferometry
Radiation Pressure Noise
Coherent Quantum Noise Cancellation (CQNC)
Limitations to CQNC
May 2013 OIST Workshop Okinawa 4
May 2013 OIST Workshop Okinawa 5
Interferometric GWDs are quite complex systems
„Free running“ they are not ready for measurement due to fluctuations (= noise)
→ GWD needs to be held in a very delicate state in many ways at all times (= controlled)!
What noise? And how to control?
GWs are quadrupole waves → effect on a ring of test masses:
GWs are very weak → 1 km baseline only changes by 1‰ of a proton diameter (10-18 m)
May 2013 OIST Workshop Okinawa 6
laser
beam- splitter
mirror
mirror photodetector
constructive interference
destructive interference
nort
h ar
m
east arm
n·λ/4
May 2013 8 OIST Workshop Okinawa
May 2013 9 OIST Workshop Okinawa
laser system
modecleaners
Michelson interferometer with dual recycling
and folded arms
May 2013 10 OIST Workshop Okinawa
Ultra-precise laser stabilisation (in frequency, intensity and geometry)
Lowest-loss substrates and coatings Multi-state pendulum suspensions for
optics Ultra-high vacuum system Recycling techniques / arm cavities Over 250, partly nested control loops
Squeezed light injection
May 2013 OIST Workshop Okinawa 11
measures against technical noise
reduces shot noise, i.e. quantum noise
May 2013 OIST Workshop Okinawa 12
Radiation Pressure Noise (RPN) is backaction noise
Shot Noise (SN) is detection noise
...both are caused by Poissonnian photon statistics
May 2013 OIST Workshop Okinawa 13
More power reduces (relative) SN:
May 2013 OIST Workshop Okinawa 14
More power increases RPN:
RPN is backaction noise → its effect looks like a GW...
May 2013 OIST Workshop Okinawa 15
SQL
lower power
higher power
SN RPN
(Picture courtesy of S. Goßler)
May 2013 OIST Workshop Okinawa 17
...will be limited by quantum noise above ~12 Hz (private communication with S. Hild)
higher mirror masses for RPN reduction → only possible to a certain degree...
May 2013 OIST Workshop Okinawa 18
Best idea: eliminate RPN where it happens! But HOW? O.o Ponderomotive squeezing schemes
(H. J. Kimble et al., Phys. Rev. D, Vol. 65, 022002) Frequency-dependent squeezed input Variational output Squeezed variational
Or: what we’re doing!
May 2013 OIST Workshop Okinawa 19
SQL
Low power
High power SN
RPN
SQL
SN RPN
x
Interferometer sensitivity (force measurement):
Mechanical oscillator (position measurement):
(Picture courtesy of S. Goßler)
May 2013 OIST Workshop Okinawa 20
Scheme proposed by M.Tsang, PRL 105, 123601 (Sep. 2010): meter cavity field experiences backaction via opto- mechanically coupled mirror “anti-noise” from ancilla cavity field (through coupling via beamsplitter and χ(2) medium) causes destructive interference with RPN!
Theoretical schematic from M.Tsang, PRL 105, 123601 (Sep. 2010)
May 2013 OIST Workshop Okinawa 21
May 2013 OIST Workshop Okinawa
• mechanical susceptibility:
ancilla cavity susceptibility:
Constraints for ideal CQNC:
22
May 2013 OIST Workshop Okinawa 23
• Susceptibilities match to a certain power level
• Sensitivity off-resonance is increased by a factor of
with CQNC
without CQNC
May 2013 OIST Workshop Okinawa 24
• Susceptibilities match to a certain power level
• Sensitivity off-resonance is increased by a factor of
with CQNC
without CQNC
May 2013 OIST Workshop Okinawa 25
What if the susceptibilities do not match?
Can we really achieve perfect matching of χm(ω) and χa(ω)?
“Back of the envelope” estimation:
May 2013 OIST Workshop Okinawa 26
As long as we’re sideband resolved and have a large Q we still get sensitivity enhancement off-resonance
Imperfect matching of coupling ratios and reduces effect further
Imperfect phasematching → later
May 2013 OIST Workshop Okinawa 27
for (and plotted at )
ideal CQNC nCQNC “penalty”
SQL
May 2013 OIST Workshop Okinawa 28
for (and plotted at )
ideal CQNC
matched coupling
SQL
May 2013 OIST Workshop Okinawa 29
May 2013 OIST Workshop Okinawa 30
Jonathan Cripe (visiting student on DAAD stipend)
Timo Denker (PhD student)
Dirk Schütte (PhD student)
Daniel Steinmeyer (Master student)
Maximilian Wimmer (PhD student)
Klemens Hammerer (collaborator)
Mankei Tsang (collaborator)
May 2013 OIST Workshop Okinawa 31
...and come visit our poster!
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