Quantum Calculi—From Theory to Language Design

In the last 20 years, several approaches to quantum programming have been introduced. In this survey, we focus on the QRAM (Quantum Random Access Machine) architectural model. We explore the twofold perspective (theoretical and concrete) of the approach and we list the main problems one has to face in quantum language design. Moreover, we propose an overview of some interesting languages and open-source platforms for quantum programming currently available. We also provide the higher-order encoding in the functional languages qPCF and IQu of the well known Deutsch-Jozsa and Simon’s algorithms.

Perfect trees and bit-reversal permutations

One well known algorithm is the Fast Fourier Transform (FFT). An efficient iterative version of the FFT algorithm performs as a first step a bit-reversal permutation of the input list. The bit-reversal permutation swaps elements whose indices have binary representations that are the reverse of each other. Using an amortized approach, this operation can be made to run in linear time on a random-access machine. An intriguing question is whether a linear-time implementation is also feasible on a pointer machine, that is, in a purely functional setting. We show that the answer to this question is in the affirmative. In deriving a solution, we employ several advanced programming language concepts such as nested datatypes, associated fold and unfold operators, rank-2 types and polymorphic recursion.