Approximate simulation of quantum channels

Approximate Private Quantum Channels

This thesis includes a survey of the results known for private and approximate private quantum channels. We develop the best known upper bound for -randomizing maps, n + 2 log(1/ ) + c bits required to -randomize an arbitrary n-qubit state by improving a scheme of Ambainis and Smith [5] based on small bias spaces [16, 3]. We show by a probabilistic argument that in fact the great majority of ra...

Approximate method for treating dispersion in one-way quantum channels

Average-case complexity versus approximate simulation of commuting quantum computations

We use the class of commuting quantum computations known as IQP (instantaneous quantum polynomial time) to strengthen the conjecture that quantum computers are hard to simulate classically. We show that, if either of two plausible average-case hardness conjectures holds, then IQP computations are hard to simulate classically up to constant additive error. One conjecture relates to the hardness ...

Simulation of Direct Pumping of Quantum Dots in a Quantum Dot Laser

In this paper, the nonlinear rate equations governing a quantum dot laser isused to simulate the transient as well as the steady-state behaviors of the laser.Computation results show that the rate equations are capable of simulating true behaviorof a quantum dot laser. Then, the pump rates of the rate equations (which show indirectelectrical pumping of the quantum dots through a wetting layer) ...

Derandomizing Approximate Quantum Encryption Derandomizing Approximate Quantum Encryption

There are two variants of this definition. An encryption scheme is called perfect if Eve learns zero information from the ciphertext, and approximate if Eve can learn some non-zero amount of information. A perfect encryption ensures that the distributions (density matrices) of ciphertexts corresponding to different messages are exactly identical, while an approximate scheme only requires that t...