A quantum optical beam

unevenechoΛογισμικό & κατασκευή λογ/κού

30 Οκτ 2013 (πριν από 4 χρόνια και 8 μέρες)

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A quantum optical beam


Classically an optical beam
can have well defined
amplitude AND phase
simultaneously.


Quantum mechanics
however imposes an
uncertainty principle.


The deterministic classical
beam is blurred out by
quantum noise.



Uncertainty principle:



Coherent state Squeezed state


V
+
=V
-
=1


Ideal output of a low
-
noise laser


Same quantum noise
as vacuum


V
+

or V
-

< 1


Very fragile in the
presence of loss


Laser outputs are typically
very noisy at low frequency.


Measure squeezing of the
beat of the carrier with
frequencies outside this
noise bandwidth.



Sideband squeezing

Coherent

Production of squeezing


Produce squeezing in a below threshold
optical parametric amplifier (OPA)

Coherent

Production of squeezing


Produce squeezing in a below threshold
optical parametric amplifier (OPA)

Amplitude squeezed

Coherent

Production of squeezing


Produce squeezing in a below threshold
optical parametric amplifier (OPA)

Amplitude squeezed

Phase squeezed

Comparison of OPAs and OPOs


OPAs are seeded with a bright beam
whereas OPOs are vacuum seeded.


Advantages of OPAs:


Can lock the length of the resonator.


Bright squeezed output that can be
controlled in downstream applications.


Advantage of OPOs:


No classical noise coupled from the laser
into the squeezed beam.


In our two OPAs this noise is correlated and
can be cancelled by optical or electronic
means.

Recovering buried squeezing

The Poincaré sphere

The Poincaré sphere

Commutation
r
elation
s

o
f
Stokes

operators


The Poincaré sphere

Commutation
r
elation
s

o
f
Stokes

operators


Uncertainty relations

o
f Stokes operators


The Poincaré sphere

Commutation
r
elation
s

o
f
Stokes

operators


Uncertainty relations

o
f Stokes operators


Polarisation squeezing


A Stokes parameter is squeezed if its variance is
below the shot
-
noise of a coherent beam of equal
power.


Polarisation state of a

coherent beam

Polarisation state of a

coherent beam

Polarisation state of an

amplitude squeezed beam

one Stokes

parameter

squeezed

Polarisation state of a

coherent beam

Polarisation state of an

amplitude squeezed beam

one Stokes

parameter

squeezed

Polarisation state of a

squeezed beam combined

with a coherent beam

one Stokes

parameter

squeezed

[P.Grangier et al., Phys.Rev.Lett, 59, 2153 (1987)]

Polarisation state of a

coherent beam

Polarisation state of an

amplitude squeezed beam

one Stokes

parameter

squeezed

Polarisation state of a

squeezed beam combined

with a coherent beam

one Stokes

parameter

squeezed

[P.Grangier et al., Phys.Rev.Lett, 59, 2153 (1987)]

Polarisation state of two

phase squeezed beams

combined

one Stokes

parameter

squeezed

Polarisation state of a

coherent beam

Polarisation state of an

amplitude squeezed beam

one Stokes

parameter

squeezed

Polarisation state of a

squeezed beam combined

with a coherent beam

one Stokes

parameter

squeezed

[P.Grangier et al., Phys.Rev.Lett, 59, 2153 (1987)]

Polarisation state of two

phase squeezed beams

combined

one Stokes

parameter

squeezed

Polarisation state of two

amplitude squeezed

beams combined

two Stokes

parameters

squeezed

[
W. Bowen et. al. http://xxx.lanl.gov/abs/quant
-
ph/0110129

(2001)]

Summary


We have produced two reliable strongly
quadrature squeezed sources.


We produce new quantum polarisation states
and investigate their properties.


We cancel the classical noise of our input
laser beam to produce squeezing at low
frequencies.


We have produced EPR entanglement and
are presently characterising it.