It is widely understood that quantum computing has huge disruptive potential, but despite the excitement, not enough work has been done to clearly and quantitatively articulate the precise advantages that quantum computing will bring for specific use cases. It can also be challenging to estimate when and how these use cases will become relevant.

Today’s computer chips each contain billions of tiny transistors that flip between on and off states to form binary digits, or bits, strings of ones and zeros that the computers can translate into electronic information and instructions.

The idea behind a quantum computer is that it will run on qubits, which are similar to standard bits but far more flexible. Based on principles of quantum mechanics, each qubit can be both one and zero simultaneously. These properties, in theory, allow quantum computers to achieve a quantum speedup, which grows exponentially as more qubits are added to the system.

Practically speaking, this means large calculations that would take decades or centuries to complete using even modern supercomputers can be performed in minutes on a quantum machine, leading to dramatic breakthroughs in chemistry, biology, and other scientific fields.

“By the time you get to 80 qubits, you are in a place where the qubits are storing more information than the total number of atoms in the entire universe,” said Samir Kumar, general manager of Microsoft’s venture capital arm, which has invested in PsiQuantum.

PsiQuantum is a quantum computing company on a mission to build the world’s first commercially useful quantum computer and deploy it to tackle some of the greatest challenges — across climate tech, energy, pharma, defense, financial services, and beyond.

The company is already looking ahead to the problems that quantum computing may be able to solve, from calculating which catalyst for carbon sequestration can best slow climate change to mapping more efficient ways to fertilize crops and feed an ever-growing population.

PsiQuantum believes that the journey towards a useful quantum computer won't be realized by the traditional method of building a quantum computer through gradual increments in raw qubit counts and will take too long. PsiQuantum also believes the only way to create such a machine is to manufacture it in a semiconductor foundry. As a result, PsiQuantum established its goal to build a million-qubit, fault-tolerant photonic quantum computer.

The company has developed a resolute technical roadmap that centers on overcoming all the challenges that stand in the way of achieving a quantum machine with 1 million-plus qubits, right from the start. PsiQuantum is taking an existing scalable process and working to make it quantum, rather than taking a novel quantum process and working to make it scale.

“Quantum computing is the most profoundly world-changing technology uncovered to date,” said Jeremy O'Brien, CEO and Co-Founder of PsiQuantum. “It is my conviction that the way to bring this technology into reality is by using photonics. Our company was founded on the understanding that leveraging semiconductor manufacturing is the only way to deliver the million qubits that are known to be required for error correction, a prerequisite for commercially valuable quantum computing applications.”

PsiQuantum was founded in 2016 by the world’s foremost quantum computing experts, who understood that a useful quantum computer required fault-tolerance and error correction, and therefore at least 1 million physical qubits.

The company includes a growing team of world-class engineers and scientists who are working on the entire quantum computing stack, from the photonic and electronic chips, through packaging and control electronics, cryogenic systems, quantum architecture and fault tolerance, to quantum applications.

PsiQuantum’s approach to building a large-scale, fault-tolerant quantum computer involves a photonics-based architecture that enables manufacturing in a conventional silicon chip foundry.

Since its founding, PsiQuantum has hired more than 200 people to help try to develop what’s known as a silicon photonic quantum computer—essentially, a computer that runs on light.

Scalability stands as a significant benefit that sets silicon photonics apart from alternative quantum computing methods, and PsiQuantum's architecture capitalizes on this edge.

PsiQuantum chose to use photons to build its quantum computer for several reasons: (1) Photons do not feel heat and most photonic components operate at room temperature, (2) PsiQuantum’s superconducting quantum photon detectors require cooling but operate at a temperature around 100 times hotter than superconducting qubits, (3) Photonic qubits are compatible with fiber-optic networks, making it easy to route photons between local devices, (4) Photons aren’t affected by electromagnetic interference, (5) Photons have the ability to maintain quantum states for a relatively long time.

PsiQuantum struck a deal with GlobalFoundries, one of the world’s top chipmakers, in May 2021 to build its quantum chips at GlobalFoundries’ manufacturing facilities. GlobalFoundries has already started producing early versions of PsiQuantum’s chips using its standard manufacturing facilities.

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.

PsiQuantum is now building quantum chips alongside laptops and cell phone chips on GlobalFoundries’ 300-millimeter platform.

GlobalFoundries is a high-quality, premiere fab and only one of the three tier-one foundries worldwide. GlobalFoundries sells chips to more than 250 customers globally, including the U.S. Defense Department and companies such as Qualcomm, Broadcom, Bosch, and Intel.

This partnership marks a significant contrast with other quantum experiments, which rely on exotic materials and custom manufacturing.

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.

PsiQuantum has a sizable list of patents ranging from novel materials to photonic operations. “We’ve been patenting our work since the founding of the company, patenting across the entire technical spectrum, all the way to basic semiconductor processing to materials development up to quantum algorithms and everything in between—packaging, devices, photonics, CMOS electronics, cryogenic systems, error correcting codes,” said Dr. Pete Shadbolt, Chief Scientific Officer & Co-Founder of PsiQuantum.

PsiQuantum secures funding from venture capital firms, private investors, government grants, and strategic partnerships to support its research and development efforts.

Once PsiQuantum's quantum computing technology reaches a certain level of maturity, the company will likely focus on creating and commercializing specific quantum applications.

In December 2022, PsiQuantum announced a breakthrough technique for more efficiently implementing fault-tolerant quantum computations. The company expects this technique to deliver approximately a 50x improvement in the run-time efficiency of compiled applications.

In February 2023, DARPA, the Defense Advanced Research Projects Agency, announced that it has selected PsiQuantum, Microsoft, and Atom Computing to receive five-years of funding to build fault-tolerant quantum computers under its Underexplored Systems for Utility-Scale Quantum Computing (US2QC) program. DARPA wants to determine if relatively new quantum technologies such as neutral atom, topological, and photonics can be leveraged to develop a fault-tolerant quantum computer within ten years.

In March 2023, PsiQuantum announced the opening of its UK-based advanced R&D facility at STFC’s Daresbury Laboratory in the northwest of England. This effort is backed by £9 million of funding from the UK government’s Department for Science, Innovation and Technology (DSIT), and gives PsiQuantum access to one of Europe’s largest liquid-helium (approximately -270OC) cryogenic plants.

In May 2023, PsiQuantum and its fabrication partner, GlobalFoundries, were jointly awarded a $25 million grant from the U.S. Government for tooling and further development of its photonic quantum computer. The funding will be provided by the U.S. Department of Defense (DoD) through the Air Force Research (AFRL) Laboratory located in Rome, New York. This lab has been designated as the Quantum Information Science Research Center for the U.S. Air Force and U.S. Space Force.

In May 2023, SkyWater Technology, the trusted semiconductor manufacturer and foundry, announced that PsiQuantum has expanded its development agreement with the company and its plan to produce silicon photonic chips that will become part of future quantum computing systems. The companies have teamed up to develop the chips in SkyWater’s semiconductor manufacturing facility in Bloomington, Minnesota, and this engagement supports PsiQuantum’s goal to deliver a commercially viable, error-corrected general-purpose quantum computer that scales beyond one million qubits using silicon photonics.