Optimization Approaches of Bucket Brigade Quantum RAM architecture

Abstract

The need for a Quantum RAM (QRAM) is in high demand in the field of quantum computing research. The Bucket-Brigade architecture is the most conventional among the current proposed architectures. However, this architecture has a high circuit depth as well as a high complexity which makes this architecture susceptible to noise and errors. In order to address this, we present 3 approaches to modify the existing architecture. In these approaches, we will be attempting to reduce the T-Count in the circuit using ZX-Calculus. The second approach is by modifying the routing qubits quantum gates using Fredkin Gates. We will also be introducing dynamic circuits and their properties of mid-circuit measurement and feed-forward mechanism in order to further decrease the circuit depth and T-Count. Using ZX-Calculus, we observed a 15% reduction in T-Count and a 50% reduction in T-Count when employing dynamic circuits, despite the trade-offs involving the increase in the number of Clifford gates or latency in dynamic circuits.