  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, we do not need to place
any quantum devices at the nodes of the binary tree, and hence in our qRAM
architecture, the cost to maintain the coherence can be significantly reduced.
Second, our scheme is fully parallelized. Consequently, only O(n) steps are
required to access and retrieve O(2n) data in the form of quantum superposition
states. Finally, the simplicity of our procedure may allow the design of qRAM
with simpler structures.
