The experiment, led by Ziqian Li and Eesh Gupta, who contributed equally, together with senior author David I. Schuster, showcases a device in which seven distinct memory modes can be individually addressed through a single transmon qubit acting as a classical control intermediary. Crucially, the memory modes are not raw qubits exposed to the noise of the processing layer. Instead, they live inside a multimode storage cavity, and a carefully engineered buffer layer sits between the processor and the cavity, isolating the fragile stored quantum states from the nonlinear elements that make computation possible but also make errors likely.

The need for such a device is easy to appreciate when one considers how modern superconducting quantum processors actually operate. In today’s machines, every physical qubit is tied to its own dedicated control lines, readout resonators and filters. A logical qubit protected by a surface code can demand dozens of physical qubits, each with its own coaxial cable running down into the dilution refrigerator. The wiring burden grows so quickly that scaling to useful machines has become as much a problem of engineering and cryogenics as of quantum physics. A random access memory flips this picture: if quantum information can be parked in high-coherence storage and retrieved on demand through a small number of shared control channels, the number of lines required per logical qubit falls dramatically, and the logic and storage subsystems can each be optimised separately.

The conceptual foundations for quantum random access memory stretch back to 2008, when Giovannetti, Lloyd and Maccone formalised the idea of a structure that could be queried in superposition, an operation at the heart of several quantum algorithms with proven exponential advantages. Practical implementations, however, have lagged far behind their classical counterparts. Demonstration efforts in other platforms, including a 105-mode random access memory realised with atomic ensembles in 2019, showed that the principle could be realised, but superconducting processors, the leading candidate for fault-tolerant quantum computation, notably lacked an equivalent. Architectural proposals from computer scientists, including work by Baker, Schuster and Chong on memory-equipped quantum architectures, argued that the power of random access could reshape how error-corrected machines are organised, but the hardware to realise such a vision did not yet exist.

The new device closes that gap with an elegant layered design. At its heart is a multimode microwave storage cavity, a single physical object that supports many electromagnetic modes at distinct frequencies, each capable of holding a quantum state for a long time. Seamless cavities of this kind have previously achieved photon lifetimes measured in tens or even hundreds of milliseconds, far exceeding the coherence of planar transmon qubits. A single transmon, the workhorse qubit of the superconducting world, provides the address mechanism: by tuning the transmon into resonance with a selected cavity mode, the experimenters can swap a quantum state into or out of that mode while leaving the others untouched.

The crucial innovation is the cascaded architecture with its buffer layer. Directly coupling a transmon to a multimode cavity creates a problem: the strong nonlinearity of the qubit, which enables control, also pushes unwanted photons and residual excitations back into the memory, degrading the stored states through induced dephasing and other many-body effects. The team solved this by inserting an intermediate buffer mode between the processor and the storage cavity, cascading the interactions so that the storage modes are only weakly, virtually engaged during operation. The single transmon then classically addresses the seven memory modes through this buffer, addressing them one at a time while the full stack remains protected from processor nonlinearities.

The performance figures reported are striking for a first demonstration. Arbitrary random access across the eight-bit device, meaning the ability to write to or read from any chosen memory mode on demand, was achieved with an average infidelity of less than 1.5 percent per mode. The researchers did not stop at headline numbers: they characterised the dominant error processes in detail, showing that residual many-body interactions within the multimode cavity set the present error budget. This kind of honest error accounting matters enormously for the path forward, because it tells engineers exactly which physical mechanisms must be suppressed as the architecture is scaled to more modes and longer storage times.

Beyond mere storage, the architecture supports operations performed transversally within the memory module, meaning operations that act across the encoded information without spreading errors from one component to its neighbours, a key requirement for fault tolerance. Combined with the drastic reduction in control lines per logical qubit, this positions the cascaded random access memory as a candidate unit cell for fault-tolerant quantum architectures. In such a scheme, the memory module would hold many logical qubits in long-lived cavity modes, a modest number of transmons would provide address and control, and dedicated processors would operate on retrieved states, each subsystem optimised on its own terms. The authors describe the result as enabling resource-efficient control of logical qubits, separating the problems of high-speed logic and long-duration storage that currently fight for the same physical qubits.

The work also resonates with a broader trend in the field towards bosonic and multimode approaches to quantum information. Error-corrected logical qubits encoded in oscillator states, dual-rail cavity qubits with erasure detection, and high-quality-factor niobium and coaxial cavities have all advanced rapidly in recent years, with several experiments now reaching or exceeding the break-even point for quantum error correction. What has been missing is a way to organise many such high-performance memories into an addressable, switchable whole. The cascaded random access memory provides exactly that missing layer of organisation, and it does so using components, transmons, cavities and parametric couplers, that are already compatible with existing superconducting processor fabrication.

There remain, of course, substantial challenges between this eight-bit demonstration and the megabyte-scale ambitions of quantum computing. Error rates must fall further, storage times must lengthen relative to operation times, and the many-body interaction effects that dominate the current error budget must be engineered away or incorporated into error models. The researchers have made their data and simulation codes openly available through figshare, an invitation for the community to probe, reproduce and extend the results. Yet the conceptual milestone is unambiguous. Classical computing took its decisive step towards scalability when memory was separated from logic and made randomly accessible. Quantum computing has now taken an analogous step, demonstrating that a single control qubit can reach into a protected reservoir of quantum states and retrieve any one of them on demand. If the approach scales as its designers hope, the random access quantum memory may come to be seen as the moment quantum hardware began to acquire the architectural maturity that classical machines have enjoyed for decades.

Subject of Research: Demonstration of an eight-bit cascaded random access quantum memory using superconducting circuits, transmons and multimode storage cavities for scalable fault-tolerant quantum computing.

Article Title: A cascaded random access quantum memory

Article References: Li, Z., Gupta, E., Zhao, F., Banerjee, R., Lu, Y., Roy, T., Oriani, A., Vrajitoarea, A., Chakram, S., & Schuster, D. I. (2026). A cascaded random access quantum memory. Nature Physics. https://doi.org/10.1038/s41567-026-03418-w

Image Credits: AI Generated

DOI: 10.1038/s41567-026-03418-w

Keywords: quantum memory, random access memory, superconducting circuits, transmon qubit, multimode cavity, quantum computing, fault tolerance, quantum error correction, circuit quantum electrodynamics, logical qubits, cascaded architecture, quantum architecture

The launch addresses a growing divide in quantum publishing. Much of the existing literature focuses on fundamental theory, mathematical models, or highly controlled demonstrations of quantum behavior. While this work remains essential, many researchers are now confronting a different set of challenges: how to manufacture quantum devices reliably, preserve delicate quantum states, integrate optical components, reduce system noise, and operate complex platforms outside specialized research environments. AQP is positioning itself as a venue for studies that examine these practical questions alongside the underlying science, creating a bridge between quantum physics and deployable technology.

Quantum photonics uses individual particles of light, or photons, to generate, transmit, process, and measure quantum information. Unlike classical optical signals, quantum states can encode information through properties such as polarization, phase, arrival time, and path. Photons can also exhibit entanglement, a uniquely quantum correlation that links measurement outcomes even when particles are separated. These characteristics make photonic systems promising for secure communications, precision sensing, quantum computing, and the exchange of information between quantum processors. Yet the same states that give quantum systems their power are often extremely fragile, making the transition from proof-of-concept experiments to stable devices a demanding engineering task.

AQP is seeking contributions that show how quantum research can function in real technological settings. The journal will welcome work involving quantum materials, optical sources, detectors, components, architectures, and complete systems, particularly when studies explain the path from experimental result to implementation. Researchers are encouraged to describe technological context, identify engineering limitations, and discuss the applications their work could ultimately support. Such details may include the efficiency and stability of a photon source, the performance of a single-photon detector, the losses introduced by an optical circuit, or the methods used to control and measure a quantum device with high precision.

The emphasis on implementation reflects the rapid expansion of the quantum technology sector. Quantum communication platforms are being developed to distribute information through quantum states of light, while quantum sensors are being explored for applications ranging from navigation and medical imaging to geological surveys and environmental monitoring. Photonic approaches are also being investigated for quantum computing, where optical elements can generate and manipulate quantum states. In each case, progress depends not only on demonstrating a quantum effect but also on solving practical problems involving fabrication, packaging, calibration, scalability, energy consumption, and compatibility with existing telecommunications or computing infrastructure.

“ We are thrilled to invite the global research community to share their most groundbreaking discoveries in Advanced Quantum Photonics,” said Uriel Levy, the journal’s editor-in-chief. He described the publication as a dedicated platform for work emerging as quantum technologies move from foundational physics toward practical applications. According to Levy, optics and photonics are central to this transition because they provide the tools used to create, control, transmit, and detect quantum states. He also emphasized that SPIE’s peer-review process, international reach, and publishing infrastructure are intended to give authors broad visibility while maintaining rigorous scientific evaluation.

The journal’s scope is also designed to bring different communities into closer contact. Quantum research increasingly involves physicists, optical engineers, materials scientists, computer scientists, electrical engineers, manufacturers, and technology developers. An academic group may develop a new material for producing single photons, while an industrial team may be focused on integrating that material into a compact device. By encouraging contributions from industry as well as universities and national laboratories, AQP aims to highlight the full chain of development, from materials and components to demonstrations that operate under realistic conditions. Each issue is expected to include contributions from the quantum industry, including implementation and application demonstrations.

SPIE’s decision to establish the journal follows the society’s expanding involvement in quantum science and technology. The organization has added Quantum West to the Photonics West program and has also developed Quantum Catalyst, extending its conference activities into a field that is attracting major scientific and commercial investment. These initiatives provide researchers with opportunities to present emerging work, exchange technical knowledge, and build collaborations. AQP is intended to offer a natural publication route for research presented at such events, particularly studies whose focus is practical development rather than purely theoretical analysis.

The journal will also consider proposals for review articles and perspectives that evaluate progress across quantum materials, components, and systems. These contributions are expected to examine not only advances but also limitations, unresolved technical barriers, and opportunities for future research. That perspective could be especially valuable in a field where impressive demonstrations can sometimes obscure the difficulty of achieving repeatable performance at scale. Clear assessments of reliability, error sources, manufacturing constraints, and application requirements may help researchers distinguish between promising laboratory results and technologies ready for wider adoption.

For authors, SPIE is offering open-access publication at no cost during the journal’s first two years, a policy intended to increase the visibility and international circulation of accepted research. Open access allows readers to consult published studies without a subscription, potentially enabling faster exchange among academic groups, companies, policymakers, and the broader public. Manuscripts can be submitted through the SPIE Digital Library, which hosts the society’s journals, conference proceedings, and books. With quantum technologies developing across national and disciplinary boundaries, the new publication is seeking to become a central forum for research that explains not only what quantum devices can do, but also how they can be engineered to work in the real world.

Subject of Research: Applied quantum photonics, including quantum materials, components, systems, implementation challenges, and practical applications.

Article Title: SPIE Opens Submissions for Advanced Quantum Photonics, a New Journal for Applied Quantum Research

News Publication Date: 13 August 2026

Web References: SPIE; Advanced Quantum Photonics; Quantum West; Quantum Catalyst

References: SPIE announcement concerning the launch and submission opening of Advanced Quantum Photonics.

Image Credits: SPIE

Keywords

Quantum photonics, quantum technology, photonics, quantum computing, quantum communication, quantum sensing, quantum materials, optical engineering, SPIE, peer-reviewed journals, open access, applied physics

A groundbreaking study published in Applied Physics Letters by researchers at NYU Tandon School of Engineering and Brookhaven National Laboratory sheds light on substrate choices in phase formation and stability of superconducting films made from vanadium silicide. The study divulges critical insights into how the choice of substrate can significantly influence the properties of these superconducting materials, offering pathways for optimizing the structural integrity and phase purity necessary for their application in quantum technologies.

Led by Davood Shahrjerdi, a professor at NYU Tandon, the research focuses on vanadium silicide, which transitions into a superconducting state at about 10 Kelvin (approximately -263°C). This relatively higher superconducting transition temperature renders vanadium silicide a favorable material for use in quantum devices, particularly when operated at temperatures above those achievable by traditional millikelvin methods.

In the quest for producing high-quality superconducting films, the team engineered crystalline hafnium oxide substrates and juxtaposed their performance against standard silicon dioxide under controlled processing conditions. The findings revealed that hafnium oxide substrates exhibited superior chemical stability and were effective at suppressing unwanted secondary phases that could compromise the superconducting quality. However, the advantages of hafnium oxide came with a caveat, as the substrate showed signs of degradation when exposed to the highest processing temperatures.

The results highlight an essential facet of material science, emphasizing how crucial the substrate-film interface is in achieving phase-pure superconducting films. Shahrjerdi states, “Achieving phase-pure superconducting films requires careful attention to the substrate-film interface.” This assertion underscores the complex interplay between substrate design and the subsequent synthesis of materials intended for advanced applications, particularly in quantum technology.

Through atomic-resolution imaging techniques, researchers observed that hafnium oxide’s crystalline structure could potentially dictate the orientation and phase selection of the silicide grains formed on its surface. This notion introduces the tantalizing prospect of templating effects, suggesting that by carefully selecting substrate materials, researchers might refine and control phase nucleation in silicides to enhance their superconducting characteristics.

The implications of this research extend far beyond simply improving vanadium silicides. The fundamental principles uncovered — such as the necessity for chemical inertness, thermal stability, and structural ordering — offer broader design guidelines applicable to other superconducting silicide systems. These guidelines can pave the way for the development of next-generation substrates specifically tailored for quantum devices.

This investigation also complements previous efforts within the same research group aimed at innovating physical patterning techniques. Together, these advancements collectively broaden the practical design space from which quantum hardware can now emerge, moving towards the realization of fully functional quantum devices capable of revolutionizing technology.

As interest in quantum computing and materials science surges, it becomes increasingly clear that research into silicides and their properties is timely and essential. The material’s unique combination of properties allows for novel applications that could transcend traditional electromagnetism, ushering in an age of efficient, superconducting technologies.

In summary, the foundational insights gained from the study illuminate the significance of substrate selection in the synthesis of high-quality superconducting silicide films. With the successful manipulation of substrates like hafnium oxide, researchers can potentially unlock new avenues in the quantum realm, where materials react differently under conditions that push the boundaries of our known physical laws.

As researchers continue to delve into the complex world of silicides and their properties, the methods and principles from this study will undoubtedly play a critical role in the design and fabrication of materials tailored for quantum applications. The quest for superior phase-pure superconducting materials is, therefore, not merely an academic pursuit but a pivotal stride towards realizing the ambitious goals of quantum technology.

Subject of Research:
Article Title: Substrate effects on phase formation and interfacial stability in superconducting vanadium silicide thin films
News Publication Date: 23-Sep-2025
Web References: Applied Physics Letters
References: DOI 10.1063/5.0291576
Image Credits:

Keywords