The Radiant Revolution: A Short History of Photonic Quantum Computing

The field of quantum computing is evolving rapidly. Various technologies are vying to become the foundation for the next generation of computation. Photonic quantum computing, which utilizes photons (particles of light) as qubits, has emerged as a promising and distinct approach.

This method offers unique advantages. It includes the potential for operation at room temperature. There is inherent compatibility with fiber optic networks for scalability. It also provides resilience against certain types of noise. This article will explore the history of photonic quantum computing. It will highlight key milestones. It will cover the contributions of leading companies like Xanadu and PsiQuantum. Additionally, it will show recent advancements shaping the field up to 2025.  

The Dawn of Photonic Quantum Computing: Early Concepts and Foundations

The idea of using light for computation has roots in classical optics. Scientists applied quantum principles to manipulate photons for information processing. This application began to take shape in the late 20th century. The inherent quantum nature of light was crucial. Albert Einstein’s work on the photoelectric effect provided the initial spark. However, the formal exploration of photonic quantum computing as a distinct field gained momentum later. 

Early theoretical work laid the groundwork for manipulating photons as qubits. Concepts like superposition are fundamental to photonic quantum computation. In superposition, a photon can exist in multiple polarization states simultaneously. Entanglement is another key concept. It occurs when two or more photons become linked regardless of distance. The challenge was to achieve controlled interactions between photons. Photons typically do not interact strongly with each other.  

A significant theoretical breakthrough came in 2000 with the proposal of the Knill, Laflamme, and Milburn (KLM) protocol. This seminal work demonstrated that only linear optical elements could achieve universal quantum computation. These include beam splitters and phase shifters. Other necessary components are single photon sources and photon detectors. The technique of feed-forward is also crucial. The KLM protocol provided a blueprint for building complex quantum gates. It leveraged probabilistic operations. It also used post-selection based on measurement outcomes. This pivotal moment showed a viable path towards scalable photonic quantum computing.  

The Rise of Integrated Quantum Photonics

KLM and other photonic quantum algorithms required the realization of complex optical setups. This need spurred the development of integrated quantum photonics. Fabricating photonic components like waveguides, beam splitters, and detectors on a single chip offered the potential for miniaturization. It also provided stability and scalability. In the early 2010s, experiments showed that creating and manipulating single photons was feasible. Researchers also performed basic quantum operations on integrated photonic circuits.

This shift towards integrated photonics set the stage for companies like Xanadu and PsiQuantum. They emerged as leaders in the field. These companies utilized advancements in semiconductor manufacturing. They also leveraged silicon photonics. Their goal was to build powerful photonic quantum computers. These computers needed to be both powerful and scalable.  

Key Players: Xanadu and PsiQuantum

Xanadu Quantum Technologies, founded in Toronto in 2016, has focused on developing cloud-accessible photonic quantum computers. Xanadu’s approach utilizes squeezed states of light within programmable loop-based interferometers. Their open-source software platform, PennyLane, has also become widely used quantum machine learning and algorithm development tools.  

Xanadu has achieved several notable milestones:

• 2020: Published a blueprint for building a fault-tolerant quantum computer using photonic technology.  
• 2022: Reported a boson sampling experiment demonstrating a significant speedup over classical computers, claiming “quantum computational advantage”. Their Borealis quantum computer, accessible through Amazon Braket, achieved this milestone .  
• 2025: Aurora, the world’s first scalable, networked, and modular universal photonic quantum computer, was introduced. This 12-qubit machine consists of four interconnected server racks and operates at room temperature. This design showcases the potential for scaling photonic quantum computers to a data center level.  

PsiQuantum was founded in Palo Alto in 2016. It is another major player focused on building a fault-tolerant, utility-scale quantum computer using silicon photonics.

Key milestones for PsiQuantum include:

• 2021: Announced a partnership with GlobalFoundries to manufacture their silicon photonic chips .  
• 2024: Secured significant funding from the Australian and Queensland governments. This funding will be used to build the world’s first utility-scale, fault-tolerant quantum computer in Brisbane. The target completion is set by the end of 2027. They also announced plans to build their first US-based utility-scale quantum computer in Chicago, Illinois.  
• 2025: Unveiled Omega, a manufacturable chipset containing all the advanced components required to build million-qubit-scale quantum computers. PsiQuantum also advanced to the final phase of DARPA’s Underexplored Systems for Utility-Scale Quantum Computing (US2QC) program.  

Recent Advancements and the Path Forward (2024-2025)

The years 2024 and 2025 have seen continued progress in photonic quantum computing. This progress spans both hardware development and theoretical advancements.

• Scalability and Networking: Xanadu’s demonstration of Aurora in early 2025 was a significant step. It addressed the scalability challenge in quantum computing by showcasing a modular and networked architecture. PsiQuantum’s focus on leveraging semiconductor manufacturing also underscores the importance of scalable production for realizing large-scale quantum computers.  
• Error Correction: Error correction remains a critical hurdle for all quantum computing platforms. In February 2025, Photonic Inc. announced a breakthrough in error correction. They introduced a new family of Quantum Low-Density Parity Check (QLDPC) codes called SHYPS. These codes reportedly require significantly fewer qubits per logical qubit than traditional surface codes. This could potentially accelerate the timeline to useful quantum computing.  
• New Techniques and Applications: Researchers continue to explore novel techniques to enhance the capabilities of photonic quantum devices. A 2024 study on arXiv proposed “state injection” as a method to increase control and flexibility in photonic circuits. This approach could potentially lead to quantum advantage in certain machine learning tasks.  
• Industry Recognition and Investment: The UN has designated 2025 as the International Year of Quantum Science and Technology. This highlights the growing global importance of the field. Significant investments and partnerships, such as the collaboration between PsiQuantum and the Australian government, further demonstrate the increasing confidence in the potential of quantum computing, including photonic approaches.  

Challenges in Photonic Quantum Computing

Despite the significant progress, photonic quantum computing still faces challenges. Photon loss during computation and the efficiency of single-photon detectors remain critical issues. Building large-scale, fault-tolerant systems requires precise control over many photons. Developing robust error correction schemes tailored for photonic qubits is also necessary. Integrating all essential optical components onto a single chip is another ongoing challenge. These components include lasers and detectors, forming photonic integrated circuits. Achieving this at a manageable cost remains challenging.

Key Milestones in Photonic Quantum Computing

The history of photonic quantum computing is marked by crucial theoretical developments and increasingly sophisticated experimental demonstrations. Here is a timeline highlighting key milestones:

• Early 20th Century: The development of quantum mechanics and the understanding of the quantum nature of light lay the foundation .  
• 1989: Gerard J. Milburn proposes a quantum-optical realization of a Fredkin gate.  
• 2000: Knill, Laflamme, and Milburn (KLM) publish their protocol showing that universal quantum computation is possible with linear optics, single photon sources, and detectors .  
• Early 2000s: First experimental implementations of linear optical quantum computing concepts using bulk optics.  
• 2010: Aaronson and Arkhipov propose the Boson Sampling model, a restricted form of quantum computation believed to be hard for classical computers.  
• 2013: The first integrated photonic circuit for quantum information processing is demonstrated.  
• 2016: Xanadu and PsiQuantum are founded.  
• 2020: Xanadu publishes a blueprint for fault-tolerant photonic quantum computing. A team in China claims “quantum supremacy” using a photonic quantum computer called Jiu Zhang, solving a Boson Sampling problem.  
• 2022: Xanadu’s Borealis achieves “quantum advantage” in a Boson Sampling experiment.  
• 2024: PsiQuantum announces major partnerships and funding to build utility-scale quantum computers in Australia and the US.  
• 2025: Xanadu introduces Aurora, the first scalable, networked, and modular universal photonic quantum computer. Photonic Inc. announces breakthrough SHYPS error correction codes. PsiQuantum unveils its Omega manufacturable chipset for million-qubit-scale photonic quantum computers and advances in DARPA’s US2QC program .  

Photonics. The Future of Quantum + Light

The history of photonic quantum computing is a journey of innovation. It is driven by fundamental physics and propelled by the ambition to overcome the limitations of classical computation. The field has made remarkable strides from early theoretical proposals to the emergence of dedicated companies and significant technological breakthroughs.

Recent advancements in scalability indicate a promising future for photonic quantum computing. Improvements in error correction also contribute. The development of modular architectures also plays a key role. As research and development continue, the “radiant revolution” in computation may be powered by light’s very essence.