There is no doubt that if somebody can build a quantum computer of sufficient power, it will fundamentally change the world. Potentially as big a change as the internet or even digital computing itself. Which makes the news that IBM has published a roadmap that brings quantum computing technology to the point of having practical, usable quantum computing capable of generalized quantum supremacy, incredibly exciting.
So what are quantum computers again?
OK, before I dig into this, it’s probably a good idea to explain a little about quantum computers – I have inserted a quick explanation in the diagram below. But put simply, quantum computers are to classical computing what the legs of an octopus are to the two hands of a human – sometimes two hands are just not enough to complete a task. The classical solution to this is to store things or to recruit more processors. However, this gets a bit out of hand(!) as the task becomes more complicated – as it does in modeling systems involving lots of particles, for example.
Steering clear of dodgy analogies (for a moment at least), quantum computing uses the properties of quantum systems that can be measured and manipulated to solve problems. The benefit is the potential ability to handle hugely complicated problems from the natural sciences or machine learning that are costly or impossible for a classical computer. They also offer the possibility of performing tasks much more quickly. Unfortunately, this does not come without some practical challenges – not least the current batch of systems needs to be extremely cold in order to interrogate the state and manipulate it. It also needs to be somehow isolated from the outside world and free from internal contamination to avoid the introduction of errors. This noise is known as decoherence and it is a major issue that scientists have been working hard to overcome. Solving this will bring so-called fault-tolerant quantum computing.
Exhibit 1 – the what and why of quantum computing.
Setting out the roadmap brings usable quantum computing closer to reality
One of the first questions to ask IBM is, why publish the roadmap now? In a recent discussion, Bob Sutor, VP – IBM Quantum Ecosystem Development, IBM Research, simply explained it was because they can. IBM’s confidence was boosted by the recent work undertaken to increase the effectiveness of its existing quantum technology (doubling the quantum volume of its Falcon device). Plus, this new generation builds upon all the other lessons learned, giving them the confidence to publish a robust roadmap to 2024. In addition, to provide the guidance, they expect (hope) this technology will take them to practical quantum supremacy within a decade.
It’s important to stress that IBM has not made any specific claims linking its roadmap to quantum supremacy or advantage. However, it is my supposition that a device with 1,000+ qubits is getting close to practical quantum advantage, depending on the quality of the qubits. At over a million qubits, it is likely to hit supremacy, making some of the most complex quantum algorithms practical. Further, the inclusion of the word “practical” is essential – a target of quantum supremacy or advantage as defined is relatively meaningless without context. In Preskill’s definition, “supremacy” has no regard for the usefulness of the task. So, the goal here is not about “supremacy” or “advantage,” at least not in an abstract fashion, but for a computer to undertake practical quantum tasks that a digital computer cannot do at all or in a realistic/useful timeframe.
The IBM team have a more precise definition of Quantum Advantage – it will be reached when quantum computing systems can solve problems important in industry significantly faster than what can be done using classical systems alone. So the goal for IBM’s quantum computing will be to help solve real-world practical problems which can be accessed by anyone via the cloud. This takes it beyond an arbitrary goal in a lab environment on a jury rig. Also, their view of significantly faster is truly a significant improvement in speed so where, for example, a classical computer took a million seconds a quantum system would take a thousand. The emphasis of practical use and integration into real world problems extends to the wording of “quantum computing system” which IBM defines as a classical computing system augmented by one or more quantum computers. These quantum computers must be universal quantum machines that take advantage of properties like superposition and entanglement.
So what exactly does the roadmap set out?
In a recent blog by Jay Gambetta, IBM Fellow and VP of IBM Quantum, IBM sets out the road map and makes the bold statement that “a fault-tolerant quantum computer now feels like an achievable goal within the coming decade.” The fault-tolerant language, plus the number of qubits, take these computers beyond practical quantum advantage.
The roadmap (below) culminates in 2023 with a 1,121 plus qubit device (Condor) and sets out its vision for a 1 million qubit system using the Condor as a framework to build the 1M qubit device. IBM expects the quantum components to be hundreds of times smaller as they miniaturize them to enable more components to fit within the framework. With IBM’s ultimate goal being a “full-stack” quantum computer accessible via the cloud, so anyone can tap into this computing power.
Exhibit 2 – IBM’s quantum roadmap.
We see many announcements around quantum; why should I care about this one?
No matter how big quantum computing could be, every advance in quantum computing tends to be followed by a statement something along the lines of “this is fantastic but isn’t likely to happen in the next ten years.” Followed swiftly by: “no one really knows for sure when, and if, it will happen.” There is a “jam tomorrow” feel to quantum computing. Like cold fusion and jetpacks, no matter what goal has been achieved, practical use feels like a long way away. With zealots spouting a never-ending story of promise, and the technology ultimately remaining out of reach, only to drift into academic obscurity.
This announcement from IBM is different. Firstly, it sets out what they expect to happen in the next four years point by point – with the final milestone, breaking the 1,000 real qubit mark, potentially bringing practical quantum advantage – a useable quantum computer capable of doing tasks 100s or 1000s of times faster than a traditional computer, available via the cloud that companies can access and use. Indeed, IBM’s emphasis on creating a practical quantum computer is embedded in its definition of quantum advantage above – given the need for it to be able to solve real world industrial problems and integrated within a classical computing system.
Secondly, it sets a goal to deliver a computer likely to achieve practical quantum supremacy within the next decade. Using the blueprint developed with the first set of goals, IBM is building the 1M qubit machine on the same platform as Condor the 1,000+ Qubit device. If this isn’t a reason for a degree of optimism, particularly on a rainy Monday, I don’t what is. Particularly when you think this is just what IBM is doing. What is certain about IBM’s announcement is the fire it should light under the other quantum leaders like Google, Honeywell, Microsoft, Intel, Amazon, IonQ, and Rigetti. The race for a usable quantum computer is starting in earnest.
