"Others focus on intermediate milestones like “quantum supremacy” and Noisy Intermediate Scale Quantum (NISQ), aiming to build small, noisy systems and hoping to find them useful. At PsiQuantum, we chose instead to focus on the end goal: a large-scale, error corrected, general purpose quantum computer. That set us on a different path, with a different underlying technology - photonics - and a different kind of team." From PsiQuantum website.
PsiQuantum computing claims they are building an error-free photonic quantum device within the next few years.
This post covers higher-level architecture strategies that PsiQuantum employs to build a 1,000,000 error-free photonic qubit system. PsiQuantum implements "Fusion Based Quantum Computing" (FBQC) to create the error-corrected qubits at the qubit level.
They believe a fault-tolerant architecture will be required for all commercially viable applications. Imagine solving complex problems and helping humanity. Usually, with this many perfect qubits, one may wonder what would happen if someone decides to crack the RSA encryption code with a public key and a private key.
The answer is we will see many valuable algorithms in AI and optimization first before breaking the RSA with 1,000,000 qubits. Also, the gate depth in these qubits is hopefully controllable, preventing specific malicious algorithms from running.
Based on what I have read from their publications, the science team at PsiQuantum feels that any "quantum calculation" that users are doing now with the current generation of NISQ machines will only offer limited value. They think that the current generation of quantum platforms won't be able to accomplish anything worthwhile and that fighting these machines' error levels will detract from a user's focus on creating suitable algorithms to solve their problems. That may be true, but if you remember, black and white TV was introduced before color tv.
So, let's talk about their approach. PsiQuantum uses industrial semiconductor fabrication foundries to build its qubits. In the silicon photonic technology that PsiQuantum is using, precise process control is vital to minimize loss and noise in the circuit. They claim they have that worked out.
Here is the argument; when a photon travels through a channel in a piece of fabricated silicon, the walls of that channel where the photon travels at the speed of light should be as smooth and perfect as possible. Any roughness or imperfections created by the production process in the walls will result in signal loss and error, which can lead to failure. The science team at PsiQuantum, working with GlobalFounderies as a foundry partner, builds the photonic qubits based on interconnected modules, each holding x number of "perfect photonic qubits," essentially a network-ready quantum photonic system at scale. The number of qubits and how deep the gates are for each module is a proprietary method designed by PsiQuantum scientists.
I am not quite sure why PsiQuantum is not building a proof of concept platform first, instead going for the ultimate prize, which is a fault-tolerant, high-performance quantum platform that can solve the world's most pressing problems.
Building a mediocre system before creating the ultimate device may not be a good idea in the quantum computing race because it takes too much attention away from the endgame.
I am glad we had back and white TV, although the color ones were better.
https://psiquantum.com/
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