Quantum Computers Face Hurdles to Become Reliable

Scientists are actively debating whether fully functional quantum computers currently exist, a question central to the rapidly evolving field of quantum information science and technology. Liam Doyle, Fargol Seifollahi, and Chandralekha Singh, all from the University of Pittsburgh, led a study gathering expert perspectives on this critical issue and the future of quantum computing. Their research, based on in-depth interviews with leading educators in the field, addresses fundamental questions surrounding the noisy intermediate-scale (NISQ) era, the potential for truly personal quantum devices, and the most promising avenues for qubit development. The findings reveal a consensus that while current machines qualify as computers, achieving scalable, fault-tolerant systems capable of complex algorithms like Shor’s factoring algorithm remains a considerable challenge, likely decades away, and that quantum computers will likely remain specialised tools accessed remotely rather than becoming ubiquitous personal devices. These insights offer valuable guidance for educators and policymakers seeking to establish realistic expectations for this transformative technology.

Quantum computing promises to reshape computation, yet widespread practical application remains distant. Experts suggest we already have quantum computers, albeit limited ones, but fully capable machines are still years away. Understanding these timelines and realistic expectations is vital as the technology develops beyond the laboratory. Scientists explored fundamental questions frequently posed by students, the public, and the media regarding quantum information science and technology (QIST).

Through in-depth interviews, we investigated the current state of quantum computing in the noisy intermediate-scale quantum (NISQ) era and timelines for fault-tolerant quantum computers. A possible timeline for quantum advantage on Shor’s factoring algorithm was also considered, alongside promising qubit architectures for future development. Our findings reveal diverse yet convergent perspectives on these critical issues. Experts agree that current machines utilise physical qubits.

Defining quantum computation through historical analogy and architectural flexibility

Researchers consistently affirmed the existence of quantum computers, yet responses revealed nuanced perspectives on defining these machines. Several educators drew parallels with the evolution of classical computers, noting that even early 20th-century devices rightfully earned the title of “computer”. This historical context shaped their view that a quantum computer is fundamentally a machine performing computation using quantum mechanical principles, superposition, entanglement, and interference, regardless of its current limitations.

One educator reflected that defining a quantum computer is a matter of degree, much like assessing early computing devices a century ago. Further analysis identified a flexible approach to defining and implementing quantum computation. Experts highlighted that a quantum computer need not be exclusively circuit-based, suggesting openness to diverse architectures and computational paradigms.

This viewpoint acknowledges the ongoing exploration of various qubit technologies and the potential for non-traditional quantum computing approaches. Investment across multiple platforms was deemed important at this early stage of development, with quantum simulation anticipated to yield valuable results in the near future. Beyond technical definitions, educators emphasized perspective dependence in understanding what constitutes a quantum computer, as researchers, investors, and the general public likely hold differing views.

Regarding timelines for fault-tolerant computers, most experts estimated a decade for a small, functional device, extending to several decades for scalable systems capable of running Shor’s algorithm with a demonstrable advantage. This suggests a pragmatic outlook, acknowledging the substantial engineering challenges remaining before achieving widespread quantum computational power.

Projected timelines and platform diversity for realising practical quantum computation

Scientists estimate that building a small fault-tolerant quantum computer will take a decade, with scalable systems capable of running Shor’s factoring algorithm requiring several decades more. Some experts even suggest the possibility that a law of physics may ultimately prevent achieving these goals. Regarding portable quantum computers, experts envision them as specialised tools remaining in central locations like data centres, accessible remotely for specific applications where they outperform classical computers.

Quantum researchers indicate that multiple platforms, including neutral atoms, superconducting circuits, semiconducting qubits, and photonic systems, show promise, though no clear frontrunner has emerged. These insights offer valuable guidance for educators, policymakers, and the public in establishing realistic expectations for developments in this field.

Our findings can assist educators in addressing student uncertainties regarding quantum technologies, particularly during the International Year of Quantum Science and Technology. The 21st century has witnessed rapid growth in quantum information science and technology (QIST), an interdisciplinary field promising disruptive advancements in computation, communication, and sensing, leveraging quantum superposition and entanglement.

Shor’s groundbreaking theoretical work in the mid-1990s on factoring and quantum error-correction, coupled with advances in controlling microscopic systems, significantly propelled the field forward. Over the last three decades, QIST has evolved from theoretical concepts to physical implementations, with numerous companies and research institutions now operating quantum processors with diverse qubit architectures.

The current state of quantum computing is often characterised as the noisy intermediate-scale quantum (NISQ) era, a term coined by Preskill to describe processors capable of certain computations beyond classical computers, yet susceptible to decoherence and errors. This intermediate stage has generated both excitement and confusion among students and the public.

Rapid progress in QIST has attracted significant media attention, public interest, and substantial investment from governments and the private sector. However, this attention has also led to misinformation regarding the current capabilities of quantum computers, unrealistic timelines for practical applications, and confusion about promising technological approaches.

Unlike classical computers built using mature semiconductor technology, the proliferation of different qubit platforms complicates understanding of the field’s trajectory. Extensive research on student understanding of quantum mechanics informs more recent education research focused on two-state systems and QIST. Educating students and addressing public queries regarding QIST is vital for ensuring informed perspectives and realistic timelines for its growth.

Educators face challenges in conveying both the revolutionary potential of quantum technologies and the significant technical hurdles remaining to achieve quantum advantage. They must balance enthusiasm with realistic assessments of current limitations and future timelines. This paper focuses on the reflections of leading quantum researchers, who are also educators, regarding common questions from students, the public, and the media.

By capturing expert perspectives on the current state, future prospects, and practical limitations of quantum computing, we aim to provide a valuable resource for educators, policymakers, and science communicators. The researchers used structural coding for first-cycle data analysis, similar to previous approaches to organising interview data. This method labels and organises responses according to research questions, identifying larger segments of text driven by specific research questions.

Second-cycle coding identified recurring ideas or patterns across participants’ responses, grouping responses within each theme based on similarity. We ensured that nearly identical responses were condensed, presenting the response best encapsulating the idea for conciseness.

Educator perspectives temper expectations for near-term quantum computing advances

Scientists probing the future of quantum information science and technology (QIST) have uncovered a surprising degree of consensus amongst leading educators regarding timelines and realistic expectations. For years, breathless reporting has promised quantum computers in every home, or solving presently intractable problems within a few years. This work, however, reveals a more measured outlook, born from deep understanding of the engineering challenges ahead.

It’s a valuable corrective, not because it dampens enthusiasm, but because it grounds it in practicality. Acknowledging a decade or more before even a small, fault-tolerant machine appears is not simply pessimism, but reflects the sheer difficulty of scaling these systems while maintaining the delicate quantum states needed for computation. Building physical qubits is one hurdle, but controlling and correcting the errors that inevitably creep in presents a far greater one.

Experts foresee these machines remaining specialised tools, accessed remotely rather than becoming personal devices, a departure from popular depictions. The value lies in clarifying what constitutes progress. The current generation of noisy intermediate-scale quantum (NISQ) devices are computers, capable of tackling specific problems, but their limitations are clear.

Multiple qubit platforms are competing, and no single technology has emerged as the obvious frontrunner, suggesting a diverse future for the field. Once the hype surrounding quantum supremacy subsides, a more pragmatic approach to development can take hold. Now, the focus must shift towards education and workforce development. Preparing students, policymakers, and the public for the long road ahead is as important as the technological advances themselves.

Beyond the immediate challenges of error correction and scalability, fundamental questions remain about the architecture of future quantum systems and the best ways to integrate them with existing classical infrastructure. This study doesn’t offer definitive answers, but it provides a crucial framework for navigating the complex landscape of QIST and fostering realistic expectations for its transformative potential.