Stronger Superadditivity Relations for Multiqubit Systems

Priority Setting on the Path to UHC: Time for Stronger Institutions and Stronger Health Systems: Response to Recent Commentaries

channel estimation for mimo-ofdm systems

تخمین دقیق مشخصات کانال در سیستم های مخابراتی یک امر مهم محسوب می گردد. این امر به ویژه در کانال های بیسیم با ‏خاصیت فرکانس گزینی و زمان گزینی شدید، چالش بزرگی است. مقالات متعدد پر از روش های مبتکرانه ای برای طراحی و آنالیز ‏الگوریتم های تخمین کانال است که بیشتر آنها از روش های خاصی استفاده می کنند که یا دارای عملکرد خوب با پیچیدگی ‏محاسباتی بالا هستند و یا با عملکرد نه چندان خوب پیچیدگی پایینی...

Speed limits for quantum gates in multiqubit systems

We use analytical and numerical calculations to obtain speed limits for various unitary quantum operations in multiqubit systems under typical experimental conditions. The operations that we consider include single-, two-, and three-qubit gates, as well as quantum-state transfer in a chain of qubits. We find in particular that simple methods for implementing two-qubit gates generally provide th...

Stronger Error Disturbance Relations for Incompatible Quantum Measurements

We formulate three new error disturbance relations, one of which is free from explicit dependence upon intrinsic fluctuations of observables. The first error-disturbance relation is tighter than the one provided by the Branciard inequality and the Ozawa inequality for some initial states. Other two error disturbance relations provide a tighter bound to Ozawa’s error disturbance relation and one...

Zak’s Theorem on Superadditivity

This paper is concerned with an important theorem due to Fyodor L. Zak, which appeared in [Za1]: Let X ⊂ P be a (reduced and irreducible) subvariety. A k – secant space to X is a k – dimensional linear subspace of P which is spanned by k+1 points from X, the k – secant variety of X in P is the (closure of the) union of all the k – secant spaces of X. Zak denotes this space by S(X), we shall als...