Interplay between classical and quantum signals: partial trace and measurement channels

2010 ◽  
Vol 31 (6) ◽  
pp. 589-598
Author(s):  
Andrei Khrennikov ◽  
Masanori Ohya ◽  
Naboru Watanabe
Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 377
Author(s):  
Alexander Holevo

In this paper, we consider the classical capacity problem for Gaussian measurement channels. We establish Gaussianity of the average state of the optimal ensemble in the general case and discuss the Hypothesis of Gaussian Maximizers concerning the structure of the ensemble. Then, we consider the case of one mode in detail, including the dual problem of accessible information of a Gaussian ensemble. Our findings are relevant to practical situations in quantum communications where the receiver is Gaussian (say, a general-dyne detection) and concatenation of the Gaussian channel and the receiver can be considered as one Gaussian measurement channel. Our efforts in this and preceding papers are then aimed at establishing full Gaussianity of the optimal ensemble (usually taken as an assumption) in such schemes.


2019 ◽  
Vol 12 (1) ◽  
pp. 363-370 ◽  
Author(s):  
Betsy M. Farris ◽  
Guillaume P. Gronoff ◽  
William Carrion ◽  
Travis Knepp ◽  
Margaret Pippin ◽  
...  

Abstract. During the 2017 Ozone Water Land Environmental Transition Study (OWLETS), the Langley mobile ozone lidar system utilized a new small diameter receiver to improve the retrieval of near-surface signals from 0.1 to 1 km in altitude. This new receiver utilizes a single 90 ∘ fiber-coupled, off-axis parabolic mirror resulting in a compact form that is easy to align. The single reflective surface offers the opportunity to easily expand its use to multiple wavelengths for additional measurement channels such as visible wavelength aerosol measurements. Detailed results compare the performance of the receiver to both ozonesonde and in situ measurements from a UAV platform, validating the performance of the near-surface ozone retrievals. Absolute O3 differences averaged 7 % between lidar and ozonesonde data from 0.1 to 1.0 km and yielded a 2.3 % high bias in the lidar data, well within the uncertainty of the sonde measurements. Conversely, lidar O3 measurements from 0.1 to 0.2 km averaged 10.5 % lower than coincident UAV O3. A more detailed study under more stable atmospheric conditions would be necessary to resolve the residual instrument differences reported in this work. Nevertheless, this unique added capability is a significant improvement allowing for near-surface observation of ozone.


2016 ◽  
Vol 59 (3) ◽  
pp. 585-591 ◽  
Author(s):  
Minghua Lin

AbstractLet A be a density matrix in . Audenaert [J. Math. Phys. 48(2007) 083507] proved an inequality for Schatten p-norms:where Tr1 and Tr2 stand for the first and second partial trace, respectively. As an analogue of his result, we prove a determinantal inequality


Author(s):  
JEAN-CHRISTOPHE BOURIN ◽  
EUN-YOUNG LEE

We obtain several norm and eigenvalue inequalities for positive matrices partitioned into four blocks. The results involve the numerical range $W(X)$ of the off-diagonal block $X$ , especially the distance $d$ from $0$ to $W(X)$ . A special consequence is an estimate, $$\begin{eqnarray}\text{diam}\,W\left(\left[\begin{array}{@{}cc@{}}A & X\\ X^{\ast } & B\end{array}\right]\right)-\text{diam}\,W\biggl(\frac{A+B}{2}\biggr)\geq 2d,\end{eqnarray}$$ between the diameters of the numerical ranges for the full matrix and its partial trace.


2008 ◽  
Author(s):  
Scott E. Bisson ◽  
Robert W. Crocker ◽  
Thomas J. Kulp ◽  
Thomas A. Reichardt ◽  
Peter T. A. Reilly ◽  
...  
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