THE HYBRID QUANTUM ADVANTAGE
Key players insights
Quantum computing holds promises for numerous disruptive innovations that have motivated a decades-long race for a full-stack quantum system with practical applications. A so-called fault-tolerant quantum computer, the ultimate quantum machine that runs arbitrary algorithms faster than classical computers, has proven challenging to build and is currently expected to be a decade away, same as it was a decade ago.
QUANTUM ADVANTAGE IN THE NISQ ERA
As increasing efforts go into building a practical quantum computer with millions of qubits, excitement grows as to the possible applications of the devices we have today. Current systems with only 50 or 100 qubits and limited error correction capabilities are called Noisy Intermediate-Scale Quantum (NISQ) computers. In 2016, access to the first cloud-based and commercial NISQ computers became available for public use, and many more avenues for adoption have been created since. Although it is important to keep the long-term vision in mind, NISQ systems have the potential to offer an immediate socioeconomic benefit and allow for early practical adoption of a potentially disruptive technology that has been mostly seen in advanced laboratories so far. The questions arise: what quantum advantage can be realized today with qubits limited in number, connectivity, and performance? Would such NISQ systems allow the development of killer applications to be exploited today or in the near future?
NECESSITY FOR HYBRID QUANTUM-CLASSICAL RESOURCES
Using today’s limited NISQ computers for practical applications requires two additional ingredients. First, they need to be heavily integrated with classical computers, giving rise to the term hybrid quantum-classical computing. Second, they need to be fully controllable within their operation time, a major challenge even for state-of-the-art control systems. The experts agree working on hybrid systems with advanced control is the most probable way for things to escalate: each system provides an advantage on its native roles. The merging of the two worlds, classical and quantum, has become an exciting venue of interest for academia and industry alike, and things are moving fast.
VARIATIONAL QUANTUM ALGORITHM AS CANDIDATE FOR NISQ ADVANTAGE
As a clear example of hybrid computing, Variational Quantum Algorithms (VQAs) have emerged as a leading strategy towards the goal of finding a path to practical quantum advantage in the NISQ era. Such protocols are being considered for the entire plethora of applications envisioned for quantum computers, with much shorter feasibility time frames. Since current devices are limited by errors and noise, the approach is learning-based, the quantum analog of machine learning. VQAs rely on expressing the problem as parametric tasks to run on a quantum computer, with parameters that get calculated and optimized on a classical computer. The classical and quantum computers feed off each other in a learning loop that works like a machine learning algorithm, with training, cost functions, and convergence towards a solution. Each works in its native language and performs its tasks better than the other half would.
This powerful combination between quantum and classical resources allows tackling problems with exponential scaling difficulty, often impossible to solve with just classical computers. For example, already in 2017, IBM’s team used VQA to calculate the energy of molecules cumbersome to simulate on just classical resources, obtaining a real quantum advantage. In 2018 they defined the major challenges ahead for simulating bigger systems and addressed important problems of practical relevance in quantum chemistry and material science. First in the list is the improvement of the control systems for qubits and the development of advanced error mitigation schemes. For the first time, groundbreaking disruptive innovations in drug development, protein folding simulations, materials discovery and many more, seem to be only one control system away.
THE NEED FOR A QUANTUM ORCHESTRATION PLATFORM (QOP)
Although the need for an advanced real-time control system to combine and drive hybrid quantum-classical resources has been clearly recognized, its development path has been staggered with challenges and much-needed innovations. One such key innovation has been the concept of Quantum Orchestration.
All the previous milestones have been achieved with custom-built control systems, tailored to one specific use and made from scratch for that use only. Building a control stack from the ground up means using many general-purpose equipment and coding microcontrollers to tune this orchestra of boxes to work in synergy. Often the entire set of connections and codes is used to make a single operation function, and sometimes years of programming go into making a single experiment run smoothly. For research institutions this means years of time not spent in research, while for the industry it means many skilled programmers needed and tons of delays.
THE SINGLE-BOX ORCHESTRA
Fortunately, nowadays, Quantum Orchestration control systems specifically designed for hybrid quantum-classical computing are finally commercially available. With this new paradigm for quantum control, an entire orchestra comes in a single box and allows the tuning and playing of any set of notes, allowing each researcher to perform their symphonies without the need for advanced programming or electronics skills. A platform with such quantum-classical integration at the very core of its control architecture is a key ingredient for the seamless real-time execution of tomorrow’s algorithms. It allows running even the most advanced VQA out of the box, paving the way for the much needed jump forward for the field of NISQ applications. A QOP can perform any operation within the timescales of the quantum resources and can work with any of the many such quantum resources available. It sets a new standard for quantum control stacks and allows the quantum community to coalesce towards a single bright hybrid future, and it is exciting to see what will come next.
Today, researchers and developers can concentrate on their research. Today, orchestrating a NISQ computer can be done by experts and students alike. The doors are open for the disruptive innovations of the NISQ era, and the quantum advantage we were hoping to get one day is definitely NISQ, definitely hybrid, and it’s not found but orchestrated.