Quantum random access memory via quantum walk

A novel concept of quantum random access memory (qRAM) employing a quantum walk is provided. Our qRAM relies on a bucket brigade scheme to access the memory cells. Introducing a bucket with chirality left and right as a quantum walker, and considering its quantum motion on a full binary tree, we can efficiently deliver the bucket to the designated memory cells, and fill the bucket with the desired information in the form of quantum superposition states. Our procedure has several advantages. First, since the bucket is free from any entanglement with the quantum devices at the nodes on the binary tree, our qRAM architecture may be more robust against quantum decoherence. Second, our scheme is fully parallelized. Consequently, only $O(n)$ steps are required to access and retrieve $O(2^n)$ data in the form of quantum superposition states. Finally, the simplicity of our procedure may allow the design of qRAM with simpler structures.