Generation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>n</mml:mi></mml:math>-qubit <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>W</mml:mi></mml:math> states using spin torque
Amritesh Sharma, Ashwin A. Tulapurkar
Abstract
The $W$ state is a symmetrically entangled multipartite state where a single excitation is shared by all parties. It is an important resource for various quantum algorithms and communication systems, and hence, its preparation is of immense interest to the quantum information community. We examine here a deterministic scheme to prepare a $W$ state of an $n$-qubit system with all-to-all pairwise exchange interaction between $n$ qubits. This relies on sharing superposed excitations of a smaller number of $q$ qubits among others. We present a bound on the maximal jumps from $q$ to $n$ and formalize a scheme to generate the ${W}_{n}$ state in $O(logn)$ stages. We demonstrate this scheme in the context of spin-torque-based quantum computing architecture that is characterized by repeated interactions between static and flying qubits.