  Google recently announced that they had achieved quantum supremacy with 53
qubits (base-2 binaries or radix-2), corresponding to a computational
state-space of dimension 253 (about 1016). Google claimed to perform
computations that took 200 seconds on their quantum processor that would have
taken 10,000 years to accomplish on a classical supercomputer [1]. However,
achieving superposition and entanglement of 53 qubits is not an easy task given
the environmental noise that decoheres the qubits. In this paper, we claim that
one can potentially achieve a similar computational dimension with fewer qudits
(not qubits) where each qudit is of a higher radix (greater than 2) using a
photonics system (i.e. 16 qudits with radix-10). This paper is a collaborative
development between industry and NxGen Partners to explore such an approach.
There is a Raytheon technology that uses a Free-Space Optical (FSO) Fabry-Perot
Etalon that eliminates the need for adaptive optics [2, 3]. The NxGen
technology uses multiple Orbital Angular Momentum (OAM) modes as a new degree
of freedom for quantum computing and a multi-dimensional QKD [4-7]. We also
claim that the convergence of both broadband, secure communications, quantum
computing and quantum teleportation is only possible in a photonics
realization. Therefore, the use of photonic qudits allows the extension of
security and capacity of the quantum teleportation beyond what was achieved by
Chinese Micius quantum satellite [8]. Both the defense and commercial computing
industries need such quantum computing systems. A new measure is introduced
with computational state-space dimension, high-fidelity operations, high
connectivity, large calibrated gate sets, and circuit rewriting toolchains.
This new measure which we call quantum capacity is a practical way to measure
and compare progress toward improved system structure of a universal quantum
computer.
