We prove that Gaussian operations are of no use for protecting Gaussian states against Gaussian errors in quantum communication protocols. Specifically, we introduce a new quantity characterizing any single-mode Gaussian channel, called entanglement degradation, and show that it cannot decrease via Gaussian encoding and decoding operations only. The strength of this no-go theorem is illustrated...

Error exponents for single-user additive white Gaussian noise (AWGN) channels provide bounds on the rate of exponential decay of the average probability of error as a function of the block length of the random codebooks. In this paper, we only consider Gallager-type lower bounds of error exponents [1, 2]. For simplicity, we use the term “error exponent” to mean the maximum of random coding expo...

We investigate Gaussian quantum states in view of their exceptional role within the space of all continuous variables states. A general method for deriving extremality results is provided and applied to entanglement measures, secret key distillation and the classical capacity of bosonic quantum channels. We prove that for every given covariance matrix the distillable secret key rate and the ent...

For information transmission a discrete time channel with independent additive Gaussian noise is used. There is also another channel with independent additive Gaussian noise (the feedback channel), and the transmitter observes without delay all outputs of the forward channel via that channel. Transmission of nonexponential number of messages is considered (i.e. transmission rate equals zero) an...

We have examined the convergence behavior of the LSCMA in some simple environments. Algorithms such as Multi¬ Target CMA, Multistage CMA, and Iterative Least Squares with Projection can be used for this purpose. The results presented here can form a basis for analysis of these multi-signal extraction techniques. Clearly, the variance and distribution of output SINR obtained with the LSCMA is al...

New non-asymptotic upper bounds on the capacity of non-coherent multiple-input multiple-output (MIMO) Gaussian fading channels with memory are proposed. These bounds are used to derive upper bounds on the fading number of regular Gaussian fading channels and on the pre-log of non-regular ones. The resulting bounds are tight in the multiple-input single-output (MISO) spatially IID Gaussian case ...

In this work, the design of a -bit (scalar and vector) soft-decision demodulator for Gaussian channels with binary phase-shift keying modulation is investigated. The demodulator is used in conjunction with a soft-decision channel-optimized vector quantization (COVQ) system. The COVQ is constructed for an expanded ( 1) discrete channel consisting of the concatenation of the modulator, the Gaussi...

The energy detection M-ary Gaussian frequency-shift keying (FSK) system is proposed in this paper. The system performance is analyzed in additive white Gaussian noise channels, multipath channels, and in the presence of synchronization errors. The numerical results show that the M-ary modulation achieves the higher data rate than the binary modulation. However, it also results in performance de...