Excitation of squeezed States in a Transmission by a Josephson Degenerate Parametric Amplifier

Squeezed states of the radiation field can be used in several ways to increase the

sensitivity of precision

quantum radar

measurements

1

.

It is well known, that

s

queezed

state

s

2

can be

genera

ted

by a DC pumped degenerate Josephson parametric amplifier

,

(DCPJPA)

3

4

4

.

The DCPJPA consists of a Josephson Junction in series with a DC

voltage source, and

LC

parallel circuit coupled to a long lossless transmission line

5

. A

sufficiently long transmission line acts

also as an ohmic resistor with a real impedance

equal to the wave impedance of the transmission line.

A DC voltage applied to a

Josephson junction excites in the Josephson an AC current with a frequency

proporti

onal to the applied Voltage (

f

0

»

483,6 GHz/mV). Applying a DC voltage

corresponding to twice the

r

esonant frequency

f

r

of the

LC

circuit

allows to generate

squeezed photon states at

f

r

.

The problem has to be treated quantum mechanically under quantization of the

LC

circuit as well as the transmission line. Pulsed operation of the DCPJPA as well as

thermal excitation of the

transmission line

has to be considered.

A transmission line

initia

lly thermally excited and of length sufficiently large that the signal propagation time

along the transmission line exceeds the modeling time interval models an infinitely long

transmission line. For finite excitation pulse length the spectral width of the

pulsed signal

of the DCPJPA excites numerous longitudinal transmission line modes. The statistics of

the excited transmission line wave has to be investigated

Elektrotechnik Elektronik Microcontroller Ingenieurwesen Matlab und Mathematica

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