Scientists and engineers the world over are working to build a new generation of technologies based on the rules of quantum physics. Amazingly, these rules, which govern the world at the atomic scale, seem very different to those governing the macro world with which we are familiar.

Credit: Lund University

A water molecule and a tennis ball appear to obey very different rules. For example, at the quantum scale, we can never be certain about the location of an electron, we can only know the likelihood it would be somewhere in space as it orbits, say, the nucleus of a hydrogen atom.

Moreover, until it’s measured this uncertainty means we can in some instances describe the electron as being in more than one place at the same time. (To be fair that speaks to limits of the English language description of physical reality, but the phenomena are still very different!)

Since Einstein, many of these quantum laws seemed an oddity best ignored. How can a quantum object exist in two different physical states simultaneously?

But we are now starting to use these rules as a resource, launching a new technological revolution that promises to be as transformational in the 21st century as harnessing electricity was in the 19th.

Quantum computing is one of the best-known applications of this new technology. Quantum computers use the rules of quantum physics to build new kinds of machines that we expect will have capabilities beyond any conventional supercomputer.

The Heart of a Quantum Computer

Computers run programs to solve problems. This could be as prosaic as sums on a calculator or typing a letter on a word processor, or as complex as deep cryptography or analyzing the petabytes of data streaming in from the universe using radio telescopes.

These programs run ‘problem-solving recipes’ - called algorithms.

In classical computers, algorithms lay down a series of steps that use tiny electronic switches or transistors that are either on or off. These ‘bits’ of information run into the trillions in complex machines.

Classical supercomputers can crunch these bits very, very fast.

Binary Code


But what if these switches could follow different, quantum rules?

The basic building block of a quantum computer is the quantum bit, or qubit. Qubits are different to classical bits.

A classical bit can only be on or off. Qubits, however, are far more interesting. They take advantage of quantum laws where an object can exist in a superposition of two physical states at once.

While it isn’t a fully accurate analogy, it’s a bit like a switch being on and off at the same time.

In superposition, these quantum bits allow for different sorts of computer algorithms to solve completely different sorts of problems than today’s classical machines. These could be for modeling complex chemical reactions, discovering new exotic materials, or potentially even efficiently cracking online security systems.

The computer running your iPhone has billions of classical bits. In quantum tech engineers are still struggling to develop machines beyond a few dozen quantum bits.


Qubits easily lose their ‘quantumness’ and become boring, classical switches very easily. This fragility, called ‘decoherence’, is the central problem facing the field.

What Is Q-CTRL Trying to Do?

Q-CTRL is bringing the power of a field called control engineering to quantum technology to help extend the ‘quantum life’ of qubits.

By stabilizing qubits and increasing coherence times, we are accelerating the pathway to real and useful quantum computers.

What we do at Q-CTRL is help quantum hardware engineers solve some of the toughest problems that are delaying the emergence of this powerful new class of computer.

What Problem Does BLACK OPAL Solve?

Qubits and the computing hardware upon which they are based are exceptionally fragile. Over quite short periods of time, the exotic quantum phenomena that we try to put to work become washed out, making the hardware useless for quantum computing. As a result, running programs or algorithms on this hardware tend to accumulate a lot of errors quickly.

The hardware in modern classical computers, like your laptop, is so good that despite it containing billions of bits, it is unlikely to suffer a single serious error in more than a decade of continuous operation.

The longest that the best quantum hardware can run without an an error is about one-thousandth of a second. It is evident that the quantum technology community has a lot of work to do - and it is our job to help them.

Hardware error is the most serious barrier to building useful quantum computers, so Q-CTRL uses control engineering to help extend the life of quantum bits.

What Does BLACK OPAL Do?

Q-CTRL has developed a technique called quantum control, which helps stabilize quantum hardware against error, making it easier to build useful quantum machines.

By changing the way we run computations on the hardware we can make the computers more resilient against errors. These techniques are what we share in the form of software through BLACK OPAL, our first commercial product.

With BLACK OPAL, teams can access and build replacements for the normal operations performed on quantum hardware as part of a computation.

Our drop-in-replacement operations are stored in BLACK OPAL’s back-end in a library that can be accessed via our cloud-based suite. This library of solutions to extend the life of qubits and reduce errors has been developed over more than a decade of experimental research into quantum control.

These control solutions take the form of instructions to ‘intervene’ in your hardware, preventing decoherence. Depending on the hardware used by our clients, this intervention can be in the form of laser or microwave pulses.

By accessing these new operations, errors become less likely in our clients’ hardware by several orders of magnitude.

As well as relying on the best science, we’ve also focused on building an intuitive graphical interface that can help everyone in a research team or company learn how to use quantum control. It is designed to help guide a team to find out what kind of control is right for them and how to use control in their application.

We have also built machine learning into our controls and AI-powered tools that help teams build totally new control techniques tailored to their needs.

BLACK OPAL: Reduce Decoherence. Increase Fidelity. Take Control
BLACK OPAL: Reduce Decoherence. Increase Fidelity. Take Control

How Does It Work?

BLACK OPAL’s techniques allow us to reverse the loss of “quantumness” that results in errors. This is based on similar science to that used in taking a magnetic resonance image (MRI) on your knee. Similar control techniques used in medical imaging can be repurposed (and improved) for stabilizing quantum hardware.

Quantum devices like qubits are mathematically described as being similar to a spinning top. Over time the top can fall over, wobble, or precess as it loses its quantumness. (If you’ve seen it, think about the very final scene of “Inception”, starring Leonardo Di Caprio.)

Spinning Top


Other quantum objects, like individual water molecules, also have spin.

In magnetic resonance imaging, the signal comes from the collective effect of water molecules in your body. Each has a spinning top and over time they all wobble and become randomly oriented relative to one another.

This randomness degrades the signal used in imaging.

Using the right control technique realigns and “refreshes” all of those spinning tops to give a measurable signal. The physics that makes this work can now be used in quantum technology to stabilize another sort of ‘spinning top’ - an individual qubit.

Q-CTRL has developed this science to help stabilize quantum systems used in quantum computing.

What’s the Benefit?

The techniques we share in BLACK OPAL can be used to significantly reduce errors in real quantum computing hardware that is being developed around the world right now.

Published and peer-reviewed experiments - from our team and others - have demonstrated we can extend the useful lifetime of quantum hardware by more than 1000 times and reduce the likelihood of error in a single computational operation by more than 100 times.

This means a team can run a much more complex computation before the hardware fails, accelerating the pathway to develop the first useful quantum computers.

The importance of control in quantum computing is backed by powerful historical example. Control has built an industry before: in aviation.

The Wright Brothers were not the first to fly. But they were the first to achieve manned, powered, controlled flight by bringing control to the technology.

Giving pilots a high level of command over how the machine behaved allowed them to achieve what others could not. We believe that by using BLACK OPAL, control can have an equally profound impact on the development of quantum computing.

First flight of the Wright Flyer I, December 17, 1903, Orville piloting, Wilbur running at wingtip.
First flight of the Wright Flyer I, December 17, 1903, Orville piloting, Wilbur running at wingtip.

Is It for Me?

If you have basic knowledge of quantum computing (e.g. you’ve heard of a qubit) and want to learn about what quantum control is and how it can stabilize quantum hardware, BLACK OPAL is for you.

BLACK OPAL helps teams learn about and deploy quantum control. Our customers include students seeking to learn more about quantum control techniques through to professional quantum hardware manufacturers seeking to improve the performance of their hardware.

BLACK OPAL helps theorists and experimentalists build intuition about otherwise very complex control techniques and deploy them either in their research or in building new hardware.