Quantum Untangled - The code that makes the qubits useful
We need to talk about software.
The first computer program was written by Ada Lovelace in 1843 for Charles Babbage's marvellously ambitious (and tragically hypothetical) Analytical Engine. Intended to showcase the computational power of this whirring, shunting assembly of cogs and flywheels, Lovelace’s code was designed to calculate a sequence of Bernoulli numbers. Though the Analytical Engine was never completed in either Lovelace or Babbage’s lifetimes, computer science students still use Bernoulli numbers to flex their coding muscles.
Most complex machines are now equipped with a silicon chip and a coding language governing the parameters of its mission, whether they’re inside the washing machines scrubbing your clothes clean in a hundred different modes at 30°C (or higher than that, if you’re truly unhinged) or the screaming selection of children’s toys designed to delight and irritate households in equal measure. Quantum computers are no exception to this trend. Being equipped with qubits instead of bytes is all well and good, but you still need a way of telling the machine how to harness those nifty, slippery particles and define their calculations. It should be of little surprise to loyal readers, then, that more than a few companies in the quantum ecosystem are busily producing algorithms, operating systems and abstraction layers that tell the qubits what and how to perform set tasks, allowing the end user to write in Python, C++ or Q#.
A dose of quantum SaaS
To allow these languages to realise their full potential, major players in the quantum space have devised open source frameworks that include all the technology designed to run code on quantum hardware — think Qiskit from IBM, or Cirq by Google. But for a quantum computer to achieve advantage — or ‘utility’, as IBM is now calling it — the software layer needs to be even more abstract and easier to understand.
One company focusing on complete abstraction is Multiverse Computing. It offers a SaaS product called Singularity that, to the end user, appears as nothing more than another menu item in Microsoft Excel. That’s because, in the back end, Multiverse works with its clients to understand their data requirements to a point where they can be boiled down into the tailor-made, quantum equivalent of the flick of a switch.
None of this work necessarily requires a quantum computer, explains Esperanza Cuenca-Gómez, Multiverse’s head of strategy. “We use tensor networks,” says Cuenca-Gómez. “Quantum-inspired techniques use the principle of quantum mechanics and then those algorithms are deployed on high-performance classical hardware.”
Real world results are already being seen and acted on from today’s quantum systems, she adds, even though the software layer isn’t necessarily being deployed on quantum hardware right now. That said, Cuenca-Gómez claims, it’s perfectly capable of being run on tomorrow’s quantum computers as and when they’re ready.
Ghosts inside the machine
Quantum SaaS products are one thing — but the quantum ecosystems of the future will also require far larger, more complex programming frameworks to support multiple applications. Enter the quantum OS, tasked with error handling and equipped with core libraries that allow developers an easier time when contending with quantum hardware.
One of the leading quantum OS developers is Cambridge-based Riverlane. The firm’s VP of product, Maria Maragkou, is plain about the challenges her colleagues face in this kind of work. At the very least, she told me, developers have to grapple daily with the “mind-boggling quantity and quality of data quantum computers produce when performing calculations,” a process that then results in the issue of correcting “copious data errors in real time.”
Quantum computers are prone to errors and noise as a result of the nature of the way atoms and objects in the quantum realm interact. “Building software in such an environment is uniquely challenging,” Maragkou says. “In practical terms, this means a medium-sized quantum computer must ‘decode’ roughly the equivalent Netflix's total global streaming data every second – or rapidly grind to a screeching halt under the weight of errors.”
But that isn’t the end of the difficulties. Data stored on qubits, after all, can’t be measured or observed without destroying it. To solve this problem, so-called 'syndrome' qubits are needed - particles that can be used to spot data errors on the active qubits. A cluster of syndrome qubits, meanwhile, can create a single logical qubit, the holy grail of practical quantum computing.
The process of creating a syndrome qubit sounds simple, but in reality it is a complex, compute-intensive process that imposes specific challenges on developing quantum software, explains Maragkou. “Developers must also account for the fact that quantum computers typically deliver a range of possible answers,” she says, “rather than a single answer to a problem.”
Current and proposed quantum operating systems will help mitigate some of these issues. As well as creating less noisy and error-prone qubits, the software acts to control the qubits by opening and closing gates or operating the infrastructure that manipulates the particles. This, then, helps the qubits maintain their superposition. The OS then acts to decode the errors.
Having a system that works independent of the quantum hardware itself also helps. “Not all hardware companies need to develop all components uniquely and from scratch,” added Maragkou. “Secondly, interoperability and standards enabling software and applications allows developers to concentrate on that part of the stack and not worry about portability across hardware.”
Ada Lovelace said of Babbage’s machine that it “has no pretensions whatever to originate anything. It can do whatever we know how to order it to perform.” That premise still stands today, but with quantum computing, its output isn’t as straightforward as the ones and zeros of that early analogue computer.
Nevertheless, it’ll be through software, rather than hardware, that we will use to engage with quantum machines, in much the same way as we do with conventional computers today. For most people, this will consist of interacting with applications running on classical machines, or if they possess the requisite coding skills, through a simple Python script in a Jupyter notebook. Whatever form that engagement will take, I suspect that, sooner than we think, we’ll all be talking a lot more about the quantum software industry than the qubits and gateways buried inside the hardware.
The best of the rest
It would be remiss of me to leave you daydreaming about the potentiality of quantum software without mentioning a couple of other pieces on the quantum landscape Tech Monitor’s published this week, and a little news of my own:
Quantum encryption seeks its first – and final – frontier
Quantum computers pose an existential threat to standard forms of encryption and, with that, the future of global communications as we know it. Little wonder, then, that the satellite industry has started preparing for what’s next. This week our valiant feature writer, Stephanie Stacey, guides us through the sector’s experiments with post-quantum encryption and QKD, and how these dalliances with the bleeding edge of cryptography are set to transform the security undergirding our lines of communication.
IBM to launch first European quantum data centre
Here’s you thinking, all innocently enough, that we’re about to enter into a blissful future where businesses can communicate seamlessly with quantum clouds situated in any country without worrying about data protection laws. Well, who looks silly now? Anticipating that very challenge, IBM has announced its first European data centre, the construction of which will help the firm address any concerns regional authorities might have about GDPR enforcement in the quantum landscape.
And finally…
Come see me at next week’s Quantum Computing Summit in London! I’ll be presenting a panel about the need for us all to begin thinking about ethical quantum computing, and how the kinds of risks we’re now very publicly discussing about AI could carry over to the world of quantum computing. Find a blurb here and register your attendance here!
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