When Will Quantum Computing Have Its ENIAC Moment?

  • ENIAC moment. The stage at which a nascent technology is finally able to demonstrate that it is capable of solving a significant real-world problem — actually solving a problem and delivering substantial real-world value, in a manner which is a significant improvement over existing technologies. The moment when promises have been fulfilled.


Quantum computing will not have its ENIAC moment any time soon, but it is likely, in my own personal view, within five to seven years, and maybe even in four, or possibly even three years if we’re really (really!) lucky.

Summary of main issues

To summarize the main issues that are currently precluding an ENIAC moment for quantum computing any time soon:

  1. Need a lot more qubits — 500 to 1,000 rather than the current 50 to 100. And with support for a universal gate set supporting arbitrary quantum circuits on those qubits — special-purpose, single-function quantum computers won’t constitute an ENIAC moment.
  2. Need significantly longer coherence time — milliseconds rather than microseconds.
  3. Quantum error correction? May be needed eventually, but not for an ENIAC moment. A focus on reasonably stable qubits, longer coherence time, and reasonable environmental shielding is probably sufficient for an ENIAC moment.
  4. Need greater connectivity between more combinations of qubits — for entanglement.
  5. Need more and richer hardware features.
  6. Need more and richer firmware features. Including basic numeric math features and some uniquely quantum features such as quantum Fourier transform and phase estimation.
  7. Need better methods and tools for transforming classical-style algorithms to exploit the oddities of quantum computers and to exploit quantum parallelism.
  8. Need at least a healthy subset of the features of classical Turing machines, if not the full set of Turing machine features, merged and blended with the unique features of quantum computers. Maybe not a true, fully hybrid machine, but reasonably close.
  9. Need a few killer applications which really do show a distinctive quantum advantage over classical computing — and are not relatively trivial toy applications with very trivial amounts of data. And… they must be applications which the general public can relate to and appreciate as compelling. Unless the general public is stunningly captivated, there will be no ENIAC moment.
  10. A distinctive quantum advantage means that the application would not be practical on even a relatively large classical supercomputer or even a relatively large distributed network of classical computers. Or, at a minimum, the quantum program runs at least ten to a hundred if not a thousand times faster than a comparable algorithm on a reasonably fast classical computer.

ENIAC contemporaries

There were some other, but more specialized computers over the five years preceding ENIAC, including electromechanical relay-based computers from Bell Labs, IBM, Harvard, and the German Z3 developed by Konrad Zuse in Germany in the 1940 to 1945 perod during World War II, and the Atanasoff-Berry computer (ABC, 1942) and British Colossus code-breaking computers (1943 to 1945) based on vacuum tubes, as ENIAC was, but ENIAC was a more general-purpose digital computer and made quite an impressive splash.

ENIAC very limited, but an essential critical mass

ENIAC actually had rather limited capabilities, but helped to lay the groundwork for a number of more powerful and even more general-purpose computers in the subsequent five years, including the MIT Whirlwind, EDVAC, and EDSAC in 1949. The rest is history, as they say — see more of the history in my paper Criteria for Judging Progress of the Development of Quantum Computing. But ENIAC was the key milestone which clearly signaled that electronic digital computing had finally arrived and was no longer merely a vague promise of some distant future.

General purpose even if an initial target application

ENIAC was designed initially for calculation of artillery firing tables, and later used to help design nuclear weapons. It did indeed have a specialized purpose at the very beginning, but its actual capabilities were far more general than that singular initial purpose.

General purpose is key

The goal of an ENIAC moment is not to replicate the specific computational capabilities of ENIAC per se, but to replicate its general-purpose nature as being applicable to a relatively wide and diverse range of applications — and to have sufficient computational resources to be able to handle a nontrivial amount of data.

Minimal capacity

ENIAC could perform hundreds of multiplications or thousands of additions and subtractions per second for up to twenty 10-digit numbers. That’s nothing by today’s standards but could easily replace an entire room full of human “computers” back in those days.

General-purpose programming

ENIAC required manual programming with wires and plugboards, and function tables with selector switches, but the machines which immediately followed over the subsequent five years did indeed have true, stored program capabilities. Still, programming was possible in ENIAC.

Need Turing machine capabilities

Even worse, quantum computers lack the sophisticated Turing machine computing capabilities of even the simplest classical computers.

Radical redesign of classical algorithms needed

The unfortunate and very ugly truth is that traditional or modern algorithms must be radically redesigned to cast them in terms of the basic physics operations of a quantum computer.

Probabilistic vs. deterministic

Even worse, all of us have gotten spoiled by the reliable determinism of classical computers, while even the best quantum computers promise only to deliver probabilistic computational results.

Special purpose quantum computers don’t cut it

Although there is a special-purpose quantum computer from D-Wave Systems which has 2048 qubits, it is functionally limited to quantum annealing using Ising and QUBO (Quadratic Unconstrained Binary Optimization) models for discrete optimization, and it doesn’t have even the very limited programming features of ENIAC, let alone the features of a universal gate set, common on virtually all other quantum computers.


Okay, all existing (and promised near-term) quantum computers operate essentially as coprocessors, requiring any data storage, data preparation, and result post-processing to be handled exclusively by classical software running on a classical computer, over a network connection, but at least the features of a universal gate set provide some degree of logic which isn’t available on the special-purpose, single-function D-Wave systems.

Need more qubits

The largest announced general-purpose quantum computers here in early 2019 have 49 to 160 qubits. That’s a truly impressive advance for quantum computing over the past five years, but still falls far short of the 700 qubits needed to represent the twenty 10-digit numbers which ENIAC could handle with ease — back in 1946.

Exploiting commercially-available components

To be fair, the electronic digital computers of the 1940’s had a head start which quantum computers currently don’t have — they were able to take advantage of the commercially-available vacuum tubes which had been developed over the preceding two decades for commercial radio and military applications.

Rolling your own qubits

Meanwhile, today, every quantum computer creator must develop their own basic qubits from scratch — no qubits are available commercially available off the shelf.

Perfecting basic qubits

The really big task in front of the quantum hardware guys right now is inventing and perfecting basic qubits which have far greater coherence and can be produced and controlled in much more substantial volumes.

Difficulty of designing quantum algorithms

Even then, with 500 to 1,000 robust qubits, the biggest deficits will be on the algorithmic front, with the twin deficits of the difficulty of redesigning algorithms to exploit quantum parallelism as well as the lack of the basic features of a Turing machine.

Lack of basic math

The extreme difficulty of performing even basic numerical calculations on a quantum computer poses a significant obstacle to their use for other than the most extreme niche applications where pure numeric calculations are either unneeded or worth the extreme effort.

Lack of special math functions

As another example, the ability to calculate square roots was built into the hardware of ENIAC.

Universal quantum computers

Whether we actually have to achieve a true, full, universal quantum computer, combining the features of both a pure quantum computer and the Turing machine and other advanced capabilities of a classical computer, to claim the status of a quantum ENIAC is debatable — after all, ENIAC lacked quite a few of the features of future machines which we would consider essential today, or even in 1956, a mere ten years after ENIAC was unveiled.

Critical mass of features needed

I wouldn’t insist that an ENIAC-class quantum computer must have all of these features and be the end-all of quantum computing, but I would insist that it have at least a minimal critical mass of such features which is at least indicative of the level of features to come shortly, in much the same way that ENIAC in 1946 was the precursor of Whirlwind, EDVAC, and EDSAC of 1949.

Applications ripe for quantum computing

There is still the unresolved issue of exactly what applications would make sense for an ENIAC moment for quantum computing.

Killer app for quantum computing

In short, the question remains what exactly is the killer app for quantum computing?

Classical computers are a tough act to follow

Maybe the ultimate issue here is that classical computers are a really tough act to follow.

Quantum parallelism is difficult to exploit

Quantum parallelism has great promise, but at present that promise is simply too far beyond both our reach and our grasp.

And then the ENIAC moment arrives

Only then, when all (or most) of the aforementioned issues have been addressed, will we have the quantum equivalent of ENIAC for quantum computing.

Shor’s factoring algorithm as an ENIAC moment

If somebody did manage to develop an 8K-qubit quantum computer and get Shor’s factoring algorithm running on it, cracking 2048-bit public key encryption would indeed be a true ENIAC moment, capturing everybody’s attention.

No, the IBM Q System One was not a candidate for The ENIAC Moment

IBM unveiled the IBM Q System One in January 2019, billing it as “the world’s first integrated universal approximate quantum computing system designed for scientific and commercial use.” That certainly sounds impressive. But… with only 20 qubits, and noisy qubits at that, it doesn’t even come remotely close to the level of capabilities one would properly expect for The ENIAC Moment of quantum computing — when, as I stated at the outset, a quantum computer is finally capable of solving a substantial, nontrivial, real-world computing problem with nontrivial amounts of data rather than being merely yet another promise and mere hint of a future to come, some day, but not real soon.

  • IBM Unveils World’s First Integrated Quantum Computing System for Commercial Use
  • IBM to Open Quantum Computation Center for Commercial Clients in Poughkeepsie, NY
  • YORKTOWN HEIGHTS, N.Y., Jan. 8, 2019 /PRNewswire/ — At the 2019 Consumer Electronics Show (CES), IBM (NYSE: IBM) today unveiled IBM Q System One™, the world’s first integrated universal approximate quantum computing system designed for scientific and commercial use. IBM also announced plans to open its first IBM Q Quantum Computation Center for commercial clients in Poughkeepsie, New York in 2019.
  • https://newsroom.ibm.com/2019-01-08-IBM-Unveils-Worlds-First-Integrated-Quantum-Computing-System-for-Commercial-Use

ENIAC moment in five to seven years

I’m not holding my breath, but I remain hopeful that we might see a quantum-equivalent of ENIAC within the coming decade. Just not in the next few years.

Best qubit technology?

There are a number of technologies for implementation of qubits currently used, under development, or contemplated, including superconducting quantum interference devices (SQUIDs), trapped ions, photonics and squeezed light, topological qubits, etc.

Secret labs?

Granted, somebody may be working on exactly such a machine in a secret lab right at this moment, possibly under contract to NSA or DOE — or the Chinese government, but the best I can do is to stick to publicly-disclosed details and my own experience, expertise, knowledge, intuition, and judgment.

Quantum Advantage and Quantum Supremacy

Arrival the the ENIAC moment will imply that quantum computing has also achieved so-called quantum advantage. The terms quantum advantage and quantum supremacy are still a bit vague and unsettled, but for our purposes here, the mere fact that the quantum computer outperforms the best we can do for a comparable classical algorithm is the telltale sign of quantum advantage.

Quantum computing landscape continues to evolve

But stay tuned! … But don’t hold your breath.



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