Quantum computers promise to solve certain problems that would overwhelm conventional machines, but today’s systems remain limited by noise, restricted connectivity and the difficulty of scaling up the number of usable quantum bits. The basic unit of quantum information, the qubit, can occupy a superposition of zero and one until it is measured. Qubits can also become entangled, creating correlations that have no classical equivalent and that underpin many quantum algorithms. In practice, however, quantum states are fragile. Imperfect control pulses, unwanted interactions with the environment and errors in measurement can quickly destroy the information a computation is meant to preserve. Building a useful machine therefore requires not only more qubits, but also exceptionally precise control and sophisticated methods for detecting and correcting errors.

Neutral-atom quantum computing has emerged as one of the most closely watched approaches to these challenges. In Shunkai, individual atoms serve as qubits and are held in place by optical tweezers: tightly focused laser beams that create microscopic traps near their focal points. Because the atoms are electrically neutral, they do not need to be embedded in a solid-state circuit or cooled to extremely low temperatures to remain trapped. The system can therefore operate at room temperature in its surrounding laboratory environment, avoiding the large refrigerators required by many superconducting quantum computers. The atoms themselves are cooled and controlled using specialized laser systems, but the computing platform does not depend on a dilution refrigerator surrounding the processor.

The architecture also offers a flexible way to create interactions between qubits. A neutral atom can encode information in two long-lived internal states, while laser or microwave pulses drive transitions between those states. To produce entanglement, selected atoms can be promoted to highly excited Rydberg states. In this state, an atom’s effective size and interaction strength increase dramatically, allowing nearby atoms to influence one another. This interaction can be used to implement quantum gates, the basic operations from which quantum algorithms are constructed. Since the atoms are held in movable optical traps, the processor can rearrange them during a calculation, bringing chosen qubits together and separating them afterward. That ability to dynamically alter the geometry of the array could provide a powerful alternative to the fixed wiring used in many other quantum architectures.

Shunkai’s “full-stack” design is central to its significance. At the lowest level, the optical system captures and moves the atoms while microwave and laser fields perform quantum operations. Cameras collect the fluorescence emitted by individual atoms after measurement, allowing the system to determine whether each qubit has ended in one state or another. Above this physical layer are the timing controls, calibration routines, data-processing tools and software that translate a user’s quantum circuit into the precise sequence of signals required by the processor. By integrating these layers, the project aims to address a problem that often receives less attention than the qubit count: the gap between a promising experimental device and a machine that outside researchers can actually program, test and compare.

The Ohmori team developed Shunkai through an industry-academic collaboration involving Hitachi, which contributed to the software stack, and Infleqtion, which contributed to the quantum processing unit stack. The system is expected to begin with approximately 50 qubits and later expand to about 500. Those numbers should not be compared directly with the headline qubit counts of every competing platform, because the usefulness of a quantum computer depends on factors including coherence time, gate fidelity, connectivity, measurement accuracy and the ability to correct errors. A smaller processor with reliable operations can be more valuable for research than a much larger device whose qubits are too noisy to support meaningful calculations. Shunkai will be partially opened to external users, allowing theorists, software developers and companies to explore algorithms, investigate error-correction strategies and evaluate potential applications.

The name Shunkai refers to Harumi Shibukawa, an Edo-period astronomer whose given name can also be pronounced “Shunkai.” Shibukawa established Japan’s first original calendar system through precise astronomical calculations. The project connects that historical achievement with the modern control of quantum states on the Bloch sphere, a geometric representation used by physicists to describe the state of a qubit. The analogy is more than symbolic: both the traditional calendar and a quantum processor depend on extracting reliable predictions from highly precise measurements and carefully controlled mathematical models. By choosing the name, the researchers are linking Japan’s early scientific independence with its effort to develop a homegrown quantum-computing capability.

The immediate scientific challenge is to determine how far the machine can be pushed before noise overwhelms the computation. Quantum error correction addresses this problem by distributing one logical qubit across many physical qubits and using carefully designed measurements to identify error syndromes without directly destroying the encoded quantum information. The process does not eliminate errors in individual atoms; instead, it detects patterns that reveal when a bit-flip, phase-flip or related fault has occurred, allowing the logical state to be repaired. Neutral-atom arrays are attractive for this task because atoms can be rearranged, redundant structures can be configured for different algorithms and additional qubits can potentially be added without redesigning a rigid chip. Demonstrating reliable error detection and, ultimately, error correction will be a decisive test of whether the platform can progress from experimental calculations to fault-tolerant computation.

The project’s longer-term plan is tied to the second stage of the Ohmori Moonshot Project, focused on a neutral-atom fault-tolerant quantum computer. By March 2031, the team aims to develop a system containing 10,000 physical qubits, with quantum error-detection and correction capabilities and access for external users. Reaching that goal will require advances across the entire machine, including laser stability, atom loading, motion control, gate fidelity, real-time feedback, imaging and software orchestration. The researchers also envision integrating Shunkai with the shared supercomputer facility at the Institute for Molecular Science to create a quantum-classical or quantum-GPU hybrid center. Such a facility would allow conventional processors to handle tasks that remain inefficient for quantum hardware while quantum processors are reserved for carefully selected subproblems.

For Japan, the activation of Shunkai represents more than the arrival of another experimental quantum processor. It establishes a national platform on which researchers can test algorithms, develop control software and study the engineering requirements of large-scale neutral-atom systems. For the global quantum community, its most important contribution may be practical: a processor that connects atomic physics with the software and user infrastructure needed for real experimentation. Neutral atoms will still have to prove that they can deliver sufficiently low error rates, stable operation and economically scalable hardware. Yet by putting a complete system into operation and preparing it for outside users, the Ohmori team is turning a rapidly advancing laboratory technology into a platform that can be challenged, improved and potentially transformed into a new route toward fault-tolerant quantum computing.

Subject of Research: Neutral-atom quantum computing and the development of Japan’s first full-stack neutral-atom quantum computer, Shunkai.

Article Title: Japan Activates Its First Full-Stack Neutral-Atom Quantum Computer

News Publication Date: August 24

References: Institute for Molecular Science, National Institutes of Natural Sciences; Cabinet Office/JST Moonshot Research and Development Program; MEXT Quantum Leap Flagship Program.

Image Credits: Takafumi Tomita

Keywords: neutral-atom quantum computer, Shunkai, quantum computing, qubits, optical tweezers, Rydberg atoms, quantum entanglement, quantum error correction, fault-tolerant quantum computing, Japan, Institute for Molecular Science

One of the pivotal insights driving progress is the natural synergy between semiconductor spin qubit technologies and the well-established infrastructure of complementary metal-oxide-semiconductor (CMOS) industry. Unlike other qubit architectures, semiconductor spin qubits inherently align with CMOS fabrication methodologies, an inheritance of the silicon-based electron spin’s compatibility with industrial processes honed over decades. This congruence grants a unique opportunity to leverage the relentless advancements in CMOS scaling, precision manufacturing, and large-scale integration, establishing a pathway toward economically viable, fault-tolerant quantum processors on a scale that was previously unthinkable.

However, while this compatibility offers great promise, it is not without significant nuances. The operational paradigms of spin qubits diverge in important ways from the standard CMOS device operations. For instance, the quantum manipulation of spins relies on delicate control over quantum coherence and entanglement, demanding materials, device architectures, and control electronics tailored to nurture and preserve fragile quantum states. This contrasts with classical CMOS devices designed primarily for digital logic and charge-based operation, necessitating adaptations in materials and fabrication processes to reconcile these differing requirements.

The integration challenge extends further when considering the co-location of qubit arrays with their associated classical control elements. Minimizing heat dissipation is critical because quantum coherence is highly sensitive to thermal noise. Consequently, the cryogenic operating conditions required for spin qubits necessitate inventive low-power classical control circuits capable of operating reliably at millikelvin temperatures or interfacing effectively with room-temperature electronics. This co-integration must be achieved without sacrificing scalability or manufacturability, posing a formidable systems-engineering puzzle that relates directly to the principles of very-large-scale integration (VLSI) perfected by the CMOS domain.

One of the striking contrasts between semiconductor spin qubits and other qubit varieties is how spin systems were conceived with CMOS compatibility in mind from their inception. Spin qubits benefit from silicon’s abundance, excellent isolation properties, and a mature industrial ecosystem, setting them apart from alternative qubits that require substantial retrofitting to meet CMOS process requirements. This foresight facilitates a streamlined transition from research prototypes to foundry-compatible devices, potentially accelerating the development cycle and commercial readiness far beyond competing quantum architectures.

To realize these ambitions, concerted collaborative efforts are imperative. Bridging the knowledge and process gaps between spin-qubit researchers and CMOS industry experts will unlock synergies that neither field could achieve independently. By melding deep quantum physics understanding with the practical manufacturing experience of silicon foundries, these partnerships pave the way for fault-tolerant quantum processors that blend exquisite quantum control with the reliability and economies of scale intrinsic to CMOS fabrication.

Addressing device variability represents another critical hurdle on the path to utility-scale quantum computers. Variability in nanoscale semiconductor structures can induce fluctuations in qubit performance, undermining the overall fidelity required for error correction protocols. The CMOS industry’s rich history in managing transistor variability through statistical process control and adaptive circuit design provides a treasure trove of strategies to tame these fluctuations within spin qubit arrays. Translating these techniques into the quantum realm demands significant innovation but offers a proven framework from which to draw inspiration.

Moreover, the control electronics for spin qubits must evolve beyond traditional CMOS transistor circuits. Quantum gate operations require precise timing, amplitude modulation, and phase control of microwave and radiofrequency signals to manipulate spin states coherently. Developing compact, cryo-compatible, low-noise electronics integrated directly on the qubit chip or its immediate vicinity presents technical challenges intertwined with CMOS integration strategies. Progress in this area will be a linchpin for scalable, economically viable quantum computing platforms.

Material considerations also play a pivotal role in the CMOS compatibility of spin qubits. The purity, isotopic composition, and defect profiles of silicon substrates can dramatically influence qubit coherence times, directly impacting performance. Advanced CMOS wafers and processes must be tailored or supplemented to maintain or enhance these material qualities essential to spin qubit fidelity, sometimes challenging standard commercial silicon processing norms.

Another dimension of complexity involves the system architecture and error correction demands inherent in fault-tolerant quantum computing. Semiconductor spin qubits must be arranged into two-dimensional lattice structures and controlled with intricate microwave pulse sequences to implement error-correcting codes robustly. Integrating these systems into CMOS-compatible hardware platforms requires careful attention to wiring density, crosstalk minimization, and thermal management strategies that exploit the scalability features of CMOS while addressing quantum-specific constraints.

The path forward is illuminated by the increasing convergence between the quantum device research community and the semiconductor industry, where innovations in silicon photonics, cryoelectronics, and advanced packaging techniques offer promising routes to overcome integration bottlenecks. These technologies can support efficient control and readout schemes that dovetail with CMOS processes, driving down the complexity and cost of quantum processor platforms.

In addition to technical challenges, the economic importance of scaling quantum processors cannot be overstated. Crossing the utility scale threshold means that quantum systems provide computational advantages that justify their production, operation, and maintenance costs. CMOS-compatible semiconductor spin qubits stand as a leading contender to achieve this milestone first, thanks to their scalability potential, material advantages, and integration pathways.

The prospect of industrial-scale production of fault-tolerant quantum processors becomes tangible as semiconductor spin qubits mature within the CMOS ecosystem. This alignment not only opens avenues for rapid fabrication and deployment but also for quality assurance, standardization, and incorporation into existing computing infrastructures. Such integration could usher quantum computing from laboratories to data centers, catalyzing transformative advances in fields ranging from cryptography to pharmaceuticals.

In conclusion, semiconductor spin qubits offer a uniquely CMOS-friendly foundation on which to construct the next generation of quantum processors. Addressing the multifaceted challenges of operation, materials, system design, and co-integration through a symbiotic relationship between quantum physicists and CMOS engineers promises to accelerate the realization of utility-scale, fault-tolerant quantum computing. This convergence not only enhances technical feasibility but also positions quantum computing at the cusp of widespread industrial adoption, heralding a new era of computational capabilities grounded in silicon’s enduring legacy.

Subject of Research: Semiconductor spin qubits and their compatibility with complementary metal-oxide-semiconductor (CMOS) technologies for scale-up toward utility-scale quantum computing.

Article Title: CMOS compatibility of semiconductor spin qubits.

Article References:
Dumoulin Stuyck, N., Saraiva, A., Gilbert, W. et al. CMOS compatibility of semiconductor spin qubits. Nat Rev Electr Eng (2026). https://doi.org/10.1038/s44287-026-00283-w

Image Credits: AI Generated

Historically, implementing high-fidelity quantum gates with neutral atoms has posed significant challenges. Quantum gates, the basic units of quantum computation, manipulate qubits that exist not simply in binary states of 0 or 1, but in superpositions of these states. This superposition allows quantum computers to perform complex computations far beyond the reach of classical machines. Conventional methods have relied predominantly on exploiting highly excited electronic states—known as Rydberg states—or on atom-atom collisions and the tunnel effect to generate the requisite quantum interactions. However, these techniques are fraught with sensitivity to fluctuations in laser intensity and environmental perturbations, undermining gate quality and scalability.

A breakthrough from the Quantum Electronics group at ETH Zurich, led by Professor Tilman Esslinger, has now demonstrated a novel approach that circumvents these constraints by leveraging geometric phases to realize a swap gate with unprecedented robustness and precision. This geometric phase is a fundamentally topological property, arising not from dynamical or environment-dependent effects but from the global configuration of the quantum system’s path through its state space. By encoding the quantum exchange operation in this phase, the gate operation becomes intrinsically shielded from noise sources such as laser intensity fluctuations, thus dramatically enhancing stability.

The swap gate plays a pivotal role within quantum circuits: it exchanges the quantum states of two qubits, effectively shuffling quantum information across the processor. For example, if qubit A initially represents the quantum state 0 and qubit B the state 1, a swap gate will interchange these states. This operation is fundamental to routing and entangling quantum information, a critical requirement for scalable quantum algorithms. While swap gates have been previously demonstrated using neutral atoms in their ground states—primarily through dynamical phases induced by tunneling and collisions—these implementations suffered from susceptibility to precise control parameters.

Geometric phases, in contrast, originate from the underlying topology of the quantum system’s evolution. A classic illustration involves electron spins: rotating a spin by a full 360 degrees restores its direction but changes its wavefunction’s phase by 180 degrees. Esslinger and colleagues harnessed this abstract quantum mechanical property by employing ultracold potassium atoms confined in optical lattices—an artificial crystal of light formed by intersecting laser beams that creates an ordered pattern of potential wells. The team’s meticulous manipulation brought atom pairs so close that their quantum wavefunctions overlapped, enabling the generation of geometric phases through the Pauli exclusion principle characteristic of fermionic potassium atoms.

The fermionic nature of potassium is a crucial ingredient in this innovation. Quantum mechanics dictates that identical fermions cannot occupy exactly the same state, and this constraint within the optical lattice facilitates the controlled acquisition of a geometric phase during the swap operation. Unlike dynamical phases, which are highly sensitive to operational speed and laser stability, the geometric phase acquired is remarkably robust against such experimental uncertainties. This inherent stability enabled the ETH Zurich team to implement swap gates that operate in under a millisecond with a stunning fidelity of 99.91%, an achievement simultaneously realized across an extraordinary 17,000 qubit pairs in parallel.

This scale of parallel quantum operation marks a significant advance towards practical quantum computing with neutral atoms. The ability to perform synchronized swap gates on this many qubits opens promising pathways for constructing large-scale quantum processors capable of complex, fault-tolerant computations. Esslinger notes that while the realization of swap gates constitutes a key milestone, integrating additional quantum control elements will be necessary to build full-fledged quantum machines. Future work envisions coupling these robust gates with sophisticated quantum gas microscopes, instruments capable of imaging and manipulating individual atoms, which would allow selective operation on specific qubit pairs within the massive array.

Further sophistication has already been demonstrated by the group, who have achieved “half”-swap gates by introducing controlled atomic collisions. These partial swaps induce quantum entanglement between qubits, a non-classical correlation imperative for quantum algorithms such as Shor’s factoring or Grover’s search. Such entangling operations extend the functional repertoire beyond state exchange to enable genuine quantum computational processes. The combination of geometric-phase-based swap gates with entangling collision gates heralds a versatile platform for designing robust, scalable quantum circuits.

This research, recently published in the prestigious journal Nature, is poised to reshape our understanding of how neutral atom quantum processors can be engineered for high-fidelity, large-scale quantum computation. The geometric phase approach exemplifies how abstract quantum mechanical concepts can translate into practical technological innovations, transcending limitations imposed by classical noise sources. It offers a compelling blueprint for future quantum devices that not only scale in qubit number but also maintain exquisite control precision essential for real-world applicability.

As quantum computing edges closer to broader impact, ETH Zurich’s developments underscore the transformative power of using neutral atoms and geometric phases to overcome existing obstacles. These findings may well catalyze a new generation of quantum processors that harness the subtle geometry of quantum states rather than relying on fragile dynamical interactions. The quest for robust, scalable quantum systems has found a strong new contender in this elegant blend of theory and experimental finesse, setting the stage for profound advances in computation, cryptography, and fundamental physics.

Subject of Research: Quantum gate implementation in neutral atom quantum computers using geometric phase-based swap gates.

Article Title: Protected quantum gates using qubit doublons in dynamical optical lattices.

News Publication Date: 8-Apr-2026

Web References: https://www.nature.com/articles/s41586-026-10285-1

References: 10.1038/s41586-026-10285-1

Image Credits: Not provided.

Keywords

Quantum computing, neutral atoms, qubits, geometric phase, optical lattice, swap gate, quantum gates, quantum exchange, fermions, quantum entanglement, ultracold potassium, quantum processor scalability

This groundbreaking study pioneers the use of holographic metasurfaces—planar photonic devices densely patterned with millions of subwavelength pixels—to transcend previous scaling limitations. The metasurfaces enable the generation of highly uniform two-dimensional optical tweezer arrays that can trap more than 100 individual strontium atoms, arranged with precision in customizable geometries and at trap spacings as tight as 1.5 micrometers. Such spatial resolution is essential for dense packing of atomic arrays required by scalable quantum processors and simulators.

The underlying innovation lies in meticulously engineered holographic metasurfaces fabricated from materials with exceptionally high refractive indices, including silicon-rich silicon nitride and titanium dioxide. These materials not only provide high optical transmission efficiencies but also allow unprecedented control over phase modulation at subwavelength scales. The team leveraged advanced numerical and analytical modeling techniques to optimize the design of these metasurfaces, ensuring minimal aberrations and uniform trap characteristics such as depth, frequency, and positional accuracy. These are critical parameters directly impacting quantum coherence and gate fidelities in neutral atom systems.

Beyond demonstrating arrays in the hundred-atom regime, the researchers dramatically showcase the scalability potential of the technique by realizing an optical tweezer array comprising 360,000 traps. This vast increase in trap count—26 times higher than the previously accepted upper limit—was made possible by the metasurfaces’ subwavelength pixel dimensions that permit fine control over light fields at a resolution unattainable by traditional diffractive optical elements. Such expansive arrays pave the way for large-scale quantum simulations of complex many-body phenomena and the development of fault-tolerant quantum processors.

This advance also circumvents several technical challenges faced by conventional tweezer array generation methods. Acousto-optic deflectors typically suffer from limited beam steering bandwidth and diffraction efficiencies, while spatial light modulators are constrained by pixel size, refresh rates, and optical aberrations. In contrast, metasurfaces offer static, highly adjustable holography with compact form factors, enabling integration with compact optical platforms and potentially facilitating on-chip quantum devices.

The realization of single-atom trapping in these metasurface-generated tweezers was validated using ultracold neutral strontium atoms, which are particularly favorable for quantum metrology due to their narrow linewidth optical transitions. The uniformity across the array in terms of trap depth and frequency ensures that atom-light interactions remain consistent across sites, minimizing decoherence and fluctuations detrimental to quantum information processing.

This research represents a convergence of nanofabrication, photonics, and atomic physics, employing state-of-the-art material science to push the frontier of neutral atom control. By leveraging the high refractive index contrast and precise patterning capabilities of modern metasurface fabrication techniques, the team overcame diffraction and optical aberration bottlenecks that have traditionally hindered array scaling.

Moreover, the work opens up intriguing prospects for engineering complex and reconfigurable tweezer geometries. Arbitrary array patterns can be encoded in the holographic metasurface designs, offering unparalleled flexibility to tailor atomic interactions and simulate exotic quantum models with customizable connectivity and dimensionality. This level of design freedom has paramount importance for quantum simulations of condensed matter systems and quantum chemistry.

The impressive trap uniformity and positional accuracy achieved in this metasurface approach rival, and in some aspects surpass, the current state-of-the-art methods employing bulk optics and modulators. Such uniformity is vital not only for scalability but also for implementing precise quantum logic operations and entanglement protocols that underpin quantum computing architectures.

Looking ahead, these metasurface-based optical tweezer arrays could be integrated with other photonic components to build complex quantum photonic architectures, enabling interfacing of trapped atoms with on-chip waveguides and detectors. The planar nature of metasurfaces makes them inherently compatible with integrated photonics, potentially facilitating large-scale quantum networks and communication platforms.

In conclusion, this breakthrough demonstrates a viable path beyond existing scaling barriers in optical tweezer technology. By combining advanced material engineering, holography, and atomic physics, the research ushers in a new era for scalable neutral atom quantum devices. The achievement of trapping single atoms in massive, highly uniform tweezer arrays sets the stage for transformative developments across quantum computation, simulation, and precision measurement disciplines.

This work not only signifies a technical tour de force but also exemplifies the power of interdisciplinary innovation, leveraging photonic metasurfaces to unlock new regimes in quantum science. The demonstrated scalability and enhanced control forge critical links toward the realization of practical, large-scale neutral atom quantum technologies, accelerating progress toward fault-tolerant quantum computing and advanced quantum simulations.

Subject of Research: Quantum optics and atomic physics focusing on optical tweezer arrays generated by holographic metasurfaces.

Article Title: Trapping of single atoms in metasurface optical tweezer arrays.

Article References:
Holman, A., Xu, Y., Sun, X. et al. Trapping of single atoms in metasurface optical tweezer arrays. Nature (2026). https://doi.org/10.1038/s41586-025-09961-5

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41586-025-09961-5

Keywords: Optical tweezers, holographic metasurfaces, single atom trapping, quantum simulation, quantum computation, quantum metrology, high refractive index materials, silicon nitride, titanium dioxide, neutral atoms, scalable quantum technologies.

Quantum entanglement — the phenomenon where two or more particles become inseparably linked such that the state of one instantaneously influences the state of another regardless of distance — sits at the heart of the immense promise quantum computers hold over classical counterparts. However, harnessing this phenomenon in practical devices requires not just maintaining coherence but also engineering precise interactions between qubits, the quantum analogues of classical bits. UNSW’s novel approach employs the nuclear spins of phosphorus atoms precisely implanted in silicon, a widely used semiconductor substrate, to store and process quantum information.

For over 15 years, the UNSW team, led by Scientia Professor Andrea Morello, has made persistent strides in harnessing phosphorus nuclear spins, which are renowned as some of the most isolated quantum objects in the solid state. The exceptionally long coherence times—on the order of 30 seconds—combined with the ability to perform quantum logic operations with fidelity surpassing 99%, position these nuclear spins as ideal qubit candidates. Yet, the intrinsic isolation that renders them so clean simultaneously impedes controlled interaction, making it challenging to engineer robust multi-qubit operations necessary for universal quantum computing.

Traditionally, entangling multiple nuclear spins required positioning them in immediate proximity so they could share the same resident electron, the quantum mediator enabling coherent coupling. Unfortunately, this proximity requirement severely limits device scalability and complicates individual qubit addressability. The new UNSW study circumvents this bottleneck by introducing an innovative mechanism whereby two nuclear spins, separated by about 20 nanometers — roughly one-thousandth the width of a human hair — become entangled through electron-mediated communication that does not necessitate their sharing the same electron.

This electron-mediated interaction can be thought of as a quantum telephone line between distant atomic nuclei. Rather than restricting qubits to a confined “room,” where interactions are limited and cannot extend beyond immediate neighbors, electrons serve as delocalized mediators capable of “reaching out” and coupling nuclear spins located in physically separated regions of the silicon lattice. The scientists demonstrated this by controlling electron exchange interactions that effectively act as quantum gates, generating entangled states even when nuclei are spatially separated beyond the reach of direct coupling.

Such a manipulation of electron wavefunctions to enable remote entanglement represents a leap forward because it aligns perfectly with current silicon fabrication technologies. The scale of 20 nanometers is directly compatible with the transistor dimensions used in modern commercial microchips, meaning this quantum architecture has the potential to be integrated within existing semiconductor manufacturing pipelines. This compatibility is crucial for transitioning quantum computing from isolated laboratory demonstrations to industrial-grade, scalable quantum processors.

The team’s approach also maintains the key advantage of phosphorus nuclear spin qubits: their exceptional coherence. Unlike other physical qubit systems prone to environmental noise and rapid decoherence, the nuclear spins in this system remain well-isolated from disruptive interactions. By leveraging electrons as controllable mediators that can be dynamically moved and shaped into elongated wavefunctions, the researchers have demonstrated fast, tunable quantum operations without sacrificing coherence, a balance that has eluded many alternative quantum platforms.

Lead researcher Dr. Holly Stemp elaborates that the electron-mediated entanglement scheme offers a powerful means to scale up quantum processors. The electron “telephones” can be switched on and off with precision, allowing selective gate operations between desired pairs of nuclei while preventing unwanted crosstalk. This flexibility paves the way not only for two-qubit entanglement but also for more complex multi-qubit architectures, by increasing the number of electrons and dynamically controlling their spatial distribution within the silicon crystal.

This scalable design also brings with it a remarkable robustness. Owing to the universal nature of electron wavefunctions and well-understood silicon fabrication processes, the architecture opens a clear route toward manufacturable large-scale quantum chips. Integrating ultra-pure silicon substrates from Japan’s Keio University and precisely implanting phosphorus atoms using advanced ion implantation techniques honed at the University of Melbourne, the study underscores the profound importance of interdisciplinary collaborations in turning quantum science into viable technology.

The implications of this research are profound. By overcoming the need for nuclear spins to be bound to a single electron and instead enabling long-distance entanglement mediated by electron exchange, the UNSW team effectively removes one of the most significant barriers to developing quantum devices scalable to millions of qubits. This breakthrough brings the vision of silicon-based quantum computers—leveraging decades of semiconductor industry expertise—much closer to reality.

Moreover, the entanglement demonstrated in this work is not only a theoretical achievement but also experimentally verifiable, marking a critical step toward practical quantum error correction schemes and fault-tolerant quantum computing. As quantum processors grow in size and complexity, maintaining high-fidelity entanglement across well-isolated qubits at industrially relevant scales will be essential to realizing the full promise of quantum advantage across cryptography, simulation, and optimization.

Professor Morello emphasizes that while this result was obtained with a pair of nuclear spins, the principles underpinning the electron-mediated interactions readily scale to many more qubits. By shaping electrons into elongated wavefunctions—akin to quantum “fingers” reaching across the chip—it becomes feasible to network distant nuclei, achieving a coherent, controllable quantum processor architecture. This represents one of the most promising pathways to breaking the current quantum computing bottleneck.

Taken collectively, the UNSW team’s pioneering demonstration of scalable, electron-exchange-mediated nuclear spin entanglement marks a monumental stride forward on the quest for practical quantum computers. It not only showcases the power of silicon quantum devices but also highlights the elegant solutions that emerge at the confluence of fundamental physics, cutting-edge materials science, and innovative engineering. The future, it seems, increasingly belongs to the quantum revolution unfolding at the atomic scale inside everyday silicon chips.

Subject of Research: Quantum entanglement of nuclear spins mediated by electron exchange in silicon quantum devices

Article Title: Scalable entanglement of nuclear spins mediated by electron exchange

News Publication Date: 18-Sep-2025

References:
DOI: 10.1126/science.ady3799

Image Credits: Tony Melov / UNSW Sydney

Keywords: Quantum computing