PsiQuantum

The right partner
When PsiQuantum announced its Series D funding a year ago, the company revealed it had formed a previously undisclosed partnership with GlobalFoundries. Out of public view, the partnership had been able to build a first-of-its-kind manufacturing process for photonic quantum chips. This manufacturing process produces 300-millimeter wafers containing thousands of single photon sources, and a corresponding number of single photon detectors. The wafer also contains interferometers, splitters, and phase shifters. In order to control the photonic chip, advanced electronic CMOS control chips with around 750 million transistors were also built at the GlobalFoundries facility in Dresden, Germany.

Photon advantages

Every quantum qubit technology has its own set of advantages and disadvantages. PsiQuantum chose to use photons to build its quantum computer for several reasons:

Photons do not feel heat and most photonic components operate at room temperature.PsiQuantum’s superconducting quantum photon detectors require cooling, but operate at a temperature around 100 times hotter than superconducting qubitsPhotonic qubits are compatible with fiber-optic networks, making it easy to route photons between local devicesPhotons aren’t affected by electromagnetic interferenceAnother major advantage of photon qubits worth highlighting is the ability to maintain quantum states for a relatively long time. As an example of light’s coherence, despite traveling for billions of years, light emitted by distant stars and galaxies reaches earth with its original polarization intact. The longer a qubit can maintain its polarized quantum state, the more quantum operations it can perform, which makes the quantum computer more powerful.

“PsiQuantum has two demanding requirements. We need a huge number of components, and we need those components to consistently meet extremely demanding performance requirements. There are very few partners in the world who can reliably achieve something like this, and we always knew that partnering with a mature manufacturer like GlobalFoundries would be key to our strategy.”

The partnership has also been beneficial for GlobalFoundries because it has gained additional experience with new technologies by adding PsiQuantum’s photonic processes to the foundry.

The end is in sight

According to Dr. Shadbolt, the original question of whether large numbers of quantum devices could be built in a foundry is no longer an issue as routinely demonstrated by its output of silicon. However, inserting new devices into the manufacturing flow has always been difficult. It is slow and it is very expensive. Nanowire single photon detectors are an example of a development that came directly from the university lab and was inserted into the manufacturing process.

PsiQuantum’s semiconductor roadmap only has a few remaining items to complete. Since a million qubits won’t fit on a single chip, the quantum computer will require multiple quantum processor chips to be interconnected with optical fibers and facilitated by ultra-high-performance optical switches to allow teleportation and entanglement of single photon operations between chips.

“What remains is the optical switch,” Dr. Shadbolt said. “You might ask why photonic quantum computing people have never built anything at scale? Or why they haven’t demonstrated very large entangled states? The reason is that a special optical switch is needed, but none exists. It must have very high performance, better than any existing state-of-the-art optical switch such as those used for telecom networking. It’s a classical device, and its only function will be to route light between waveguides, but it must be done with extremely low loss and at very high speed. It must be a really, really good optical switch.”

If it can’t be bought, then it must be built

Implementing an optical switch with the right specs is a success-or-fail item for PsiQuantum. Since a commercial optical switch doesn’t exist that fits the application needs, PsiQuantum was left with no choice but to build one. For the past few years, its management has been heavily investing in developing a very high-performance optical switch.

Dr. Shadbolt explained: “I believe this is one of the most exciting things PsiQuantum is doing. Building an extremely high-performance optical switch is the next biggest thing on our roadmap. We believe it is the key to unlocking the huge promise of optical quantum computing.”

“Even though the optical switch will obviously be a very powerful generic technology of interest to others, we are not interested in its generic usefulness. We are only interested in the fact that it will allow us to build a quantum computer that outperforms every supercomputer on the planet. That is our singular goal.”
https://www.forbes.com/sites/moorinsights/2022/09/21/psiquantum-has-a-goal-for-its-million-qubit-photonic-quantum-computer-to-outperform-every-supercomputer-on-the-planet/?sh=1664287c8db3

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