We recently achieved the second major technical milestone on our journey in photonic interconnects, our core technology that we believe will enable quantum networking between and within quantum computers. The recently achieved milestone – ion-ion interconnect entanglement – marks first-time remote entanglement in a commercial environment of two qubits. Building off our ion-photon entanglement achievement announced in February, this demonstration showcases the second out of four milestones on the path to developing photonic interconnects.
Scale: Enabling Expansive Growth Through Our Unique Architecture
IonQ's Scale: Architecture that Enables Expansive Growth
IonQ’s approach to scale relies on making engineering and architectural decisions that support performance at large qubit counts. IonQ’s strategy for scaling takes advantage of multicore operation and photonically interconnected systems.
Quantum computing is making massive strides, and at IonQ, scalability guides every technical and architectural decision we make. At the core of this mission is modularity, which is the most important enabler of efficient scalability and essential to IonQ’s ability to expand quantum processing power. IonQ’s modularity is based on connecting QPUs together to increase the total number of qubits via Photonic Interconnects, which are communication links that leverage light – or photons – to transmit quantum information between different components or quantum processors. Photonic interconnects enable qubits to be entangled across individual quantum processing units (QPUs) to form a larger, more capable quantum system. IonQ’s approach uses well understood scientific principles to network the qubits and architectures similar to today’s most powerful classical computers to achieve efficient scale.
While the science and procedure behind photonic interconnects has been understood for years in a research setting, an important endeavor for IonQ has been transitioning this technology from a lab setting to a commercial environment. The ability to reach another milestone is further evidence of the advantage of IonQ’s well understood architecture for quantum networking.
Advancing Photonic Interconnects at IonQ
At IonQ, we are bringing this technology to the technical readiness level needed to start integrating it in commercially available quantum computers. Our path to photonic interconnects consists of four main milestones, each of which expands on the previous milestone and culminates in a large-scale, networked, multi quantum processing unit (QPU) system.
Milestone 1: Ion-Photon Entanglement
The first – and one of the most challenging milestones in entangling quantum information across a network of QPUs – is generating and manipulating single photons entangled with a qubit to form a network node. Such a node must be capable of three key capabilities. First, the node must have the ability to generate “interconnect photons” entangled with the interconnect qubit. Second, the node must be capable of sending these interconnect photons through fiber optics to a detection hub. Lastly, the detection hub must be able to manipulate and measure the state of the interconnect photon to confirm ion-photon entanglement.
In February 2024, we achieved Milestone 1, marking the successful entanglement of a photon with an ion qubit, outside of an academic setting—a commercial first.
Milestone 2: Photon-Mediated Ion-Ion Entanglement
Milestone 2 expands upon Milestone 1 by entangling two ion-based qubits from separate nodes using their entangled photons. To achieve this, we are developing systems to collect interconnect photons from two different nodes, and to route these photons to a single detection hub, where they interfere and are measured, leaving an entangled state between the interconnect qubits at each node. This establishes a quantum link between the QPUs.
In September 2024, IonQ’s world-class R&D team entangled two ion-based qubits from separate trap wells using entangled photons. The IonQ team achieved remote entanglement by collecting interconnected photons from two trap wells and routing them to a single detection hub.
Milestone 3: Swapping Ion-Ion Entanglement to the QPU
After establishing this remote entanglement between interconnect qubits, Milestone 3 is to demonstrate that we can transfer this entanglement from interconnect qubits to computation qubits for more complex algorithms. This entanglement can be transferred via two-qubit swap gates to establish two entangled QPUs. With this entanglement, we can expand the number of qubits available for quantum computations.
Milestone 4: Multi-QPU Programmatic Entanglement
The final milestone is our ultimate goal of scaling photonic interconnects beyond two nodes. With many QPUs networked together in a programmatic fashion, we can execute extremely wide circuits by harnessing all of the qubits in the network, in parallel. To achieve this, we are in the process of developing single-photon switching techniques and devices, allowing us to collect interconnect photons from many interconnect qubits across many traps, to selectively entangle qubits across the network based on the parameters of the circuit.
Our Vision of Enterprise-Grade Quantum Computing: From Physics to Commercial Applications
The transition from academic theory to commercial engineering is no small feat. IonQ is taking the lead in developing scalable quantum systems that can be deployed in practical, enterprise-grade applications. With the achievement of Milestone 2, we move closer to our vision of scalability while balancing performance and reliability, setting the stage for commercial quantum networking.
As we look toward Milestone 3 and beyond, we aim to demonstrate multi-QPU systems capable of handling more complex quantum computations across networks. Our applications team is busy integrating these advancements into our roadmap for real-world quantum applications, including projects for customers like Air Force Research Laboratory (AFRL) and the Applied Research Laboratory for Intelligence and Security (ARLIS).
Our ultimate goal is to scale our quantum computing capabilities far beyond the confines of a single QPU. With photonic interconnects at the core, we are pushing the boundaries of quantum computing and leading the charge towards a networked, multi-QPU future, capable of massive scale.
Stay tuned for more updates as we continue to hit major milestones on our photonic interconnect journey.