189 research outputs found
Quantum steering for two-mode states with Continuous-variable in laser channel
The Einstein-Podolsky-Rosen steering is an important resource for one-sided
device independent quantum information processing. This steering property will
be destroyed during the interaction between quantum system and environment for
some practical applications. In this paper, we use the representation of
characteristic function for probability to examine the quantum steering of
two-mode states with continuous-variable in laser channel, where both the gain
factor and the loss effect are considered. Firstly, we analyse the steering
time of two-mode squeezed vacuum state under one-mode and two-mode laser
channel respectively. We find the gain process will introduce additional noise
to the two-mode squeezed vacuum state such that the steerable time is reduced.
Secondly, by quantising quantum Einstein-Podolsky-Rosen steering, it shows that
two-side loss presents a smaller steerability than one-side loss although they
share the same two-way steerable time. In addition, we find the more gained
party can steer the others state, while the other party cannot steer the gained
party in a certain threshold value. In this sense, it seems that the gain
effect in one party is equivalent to the loss effect in the others party. Our
results pave way for the distillation of Einstein-Podolsky-Rosen steering and
the quantum information processing in practical quantum channels
Distillation of Gaussian Einstein-Podolsky-Rosen steering with noiseless linear amplification
Einstein-Podolsky-Rosen (EPR) steering is one of the most intriguing features
of quantum mechanics and an important resource for quantum communication. The
inevitable loss and noise in the quantum channel will lead to decrease of the
steerability and turn it from two-way to one-way. Despite an extensive research
on protecting entanglement from decoherence, it remains a challenge to protect
EPR steering due to its intrinsic difference from entanglement. Here, we
experimentally demonstrate the distillation of Gaussian EPR steering in lossy
and noisy environment using measurement-based noiseless linear amplification.
Our scheme recovers the two-way steerability from one-way in certain region of
loss and enhances EPR steering for both directions. We also show that the
distilled EPR steering allows to extract secret key in one-sided
device-independent quantum key distribution. Our work paves the way for quantum
communication exploiting EPR steering in practical quantum channels
The impact of hydrogenation conditions on the temperature and strain discrimination of Type i and Type IA Bragg grating sensors
We report experimental findings for tailoring the temperature and strain coefficients of Type I and Type IA fibre Bragg gratings by influencing the photosensitivity presensitisation of the host optical fibre. It is shown that by controlling the level of hydrogen saturation, via hot and cold hydrogenation, it is possible to produce gratings with lower thermal coefficients. Furthermore, there is a larger difference between the Type I and Type IA thermal coefficients and a significant improvement in the matrix condition number, which impacts the ability to recover accurate temperature and strain data using the Type1-1A dual grating sensor
Spectral modification of type IA fibre Bragg gratings by high power near infra-red lasers
We report the first experimental measurements on the spectral modification of Type IA fibre Bragg gratings, incorporated in an optical network, which result from the use of high-power, near infrared lasers. The fibre grating properties are modified in a controlled manner by exploiting the characteristics of the inherent 1400nm absorption band of the optical fibre, which grows in strength during the Type IA grating inscription. If the fibre network is illuminated with a high power laser, having an emission wavelength coincident with the absorption band, the Type IA centre wavelength and chirp can be modified. Furthermore, partial grating erasure is demonstrated. This has serious implications when using Type IA gratings in an optical network, as their spectrum can be modified using purely optical methods (no external heating source acts on the fibre), and to their long-term stability as the grating is shown to decay. Conversely, suitably stabilised gratings can be spectrally tailored, for tuning fibre lasers or edge filter modification in sensing applications, by purely optical means
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