Quantum Computing

 Quantum Insights 

Quantum computing is complicated at best. It's also one of the most confusing new paradigms ever, with big claims and fuzzy realities. We are here to share the true insights and realities about quantum computing, so you know exactly what to expect.

Why All Quantum Computers Are Hybrids

When you say hybrid quantum computers, most of us in the business have a pretty specific definition of what that means. It’s a consistent theme for a relatively straightforward concept; using a classical computer and a quantum computer together, in some form of a collaborative, possibly iterative, effort to run a computation or solve a problem.

Yet, the reality is that every single quantum computer has to function as a hybrid system. We all need to understand that as a baseline. Classical systems are required to actually run a quantum computer.

Quantum Computers Are By Necessity Hybrids

Quantum computers are not like classical systems. We all know that after listening to the quantum experts discuss the dramatic differences in how they function. Using quantum mechanics as a fundamental approach is as different from classical systems as an abacus is from an iPhone.

For example, there are a number of operations required to actually run a program and compute a solution that classical computers must perform for a quantum computer. This is what’s known as orchestration in the quantum world.

These functions include:

•  Providing the data for the operation since quantum computers do not have databases to store data, or memory to use for processing.

•  Storing and delivering the programs and applications to the quantum computer itself.

•  Classical systems are used to develop programs or algorithms to be run on the quantum computing unit (QPU), aka the hardware.

•  Orchestrating the workflow that would coordinate all of the many subcomponents of any processing or program as it is computed by the quantum computer.

•  Classical systems aggregate, interpret, and analyze results from the iterative computations as the quantum computer processes the computation. Computing expectation values (i.e, average cost of the measurement outcome) can be completed, quite efficiently, with classical systems using linear algebraic operations.

As you can see, the reality is that any quantum computer requires an integrated classical computer to control, program and provide the results from the actual QPU and its qubits.

This is why all quantum computers are naturally hybrids.

Classical systems are required to literally control and manage the processing of the quantum computer itself, aka orchestrating the quantum computer and its processing.

How Classical Computers Bring a Quantum Computer to Action

For example, let’s look at a very simple set of basic steps involved in submitting and solving a computation on a quantum computer.

First, you need data, and a problem to solve using that data. A classical computer is used to select, prepare or format and deliver data to the QPU as part of the computation. Remember, quantum systems do not have databases or storage.

Then, you need to submit the data and the program that tells the quantum computer what computation you want to perform. The classical system orchestrates the compilation of the algorithm to map the logical qubits to the specific design of the physical qubits in the target QPU. It then submits the data and problem, then manages the progression of the computation. The logic, or software, resides on the classical system.

In case you’re wondering, the classical system uses a selection of laser beam pulses to “inject” the information and problem, and to control the QPUs processing. Remember, we are in quantum space where “energy” is the fundamental asset. We are also in a processing paradigm where iteration, or running the same problem again and again, is part and parcel of finding the diverse results that provide value. That iteration is managed by the classical system, as well.

During iteration, the QPU shares the results with the classical system, which consolidates them. Once all of the potential results are measured by the QPU, the classical system analyzes, formats, and delivers those results back to the submitter. That work is also done as part of the overall orchestration.

As we can see, Will Quantum Replace Classical truly is the wrong question. The answer to that is a resounding no.

The reality beyond the applications and computational differences points to an even greater dependence on classical systems. Without classical systems working in concert with quantum computers, we won’t have quantum computing at all.

The Many Faces of a Qubit

Not today. Physically, qubits can be any two-level system. For example, the polarization of a proton, or the spin of an electron.

Early quantum hardware vendors have implemented qubits in several physical representations, each seeking to identify the best qubit for solving problems with scale and accuracy. Some use semiconductors, other electrons or atoms (ions), still others use light or photons. Some of these qubits require supercooled environments and complete isolation, others work at room temperature and are less finicky.

The Holy Grail is to define the best qubit for processing complex problems, a qubit which can be connected to scale up to be able to solve large production problems.

The challenge then becomes how to scale with accuracy – since scaling qubits results in noise and more errors, in some qubit types. Some are limited in scale due to their connections with other qubits, some by the noise they create, other simply because of the architecture that is used to connect subsets of qubits, missing full connectivity.

The jury is still out on which qubit, or qubits, will be the ultimate winner. Many believe that different qubits will become the defacto standard for different problem types. The reality is, we still don’t have the answers. But we do have a variety of powerful options.

Types of Qubits Available Today

We are currently in what’s known as noisy intermediate-scale quantum (NISQ) era. What does that mean, other than we are in the early stages of quantum computing and have so many more amazing innovations to come?

•  Noisy refers to the current state of quantum processors. They are very sensitive to the world around them and easily experience decoherence (aka the qubit gradually loses the quantum information it encodes.) They also aren’t mature enough to include error correction.

•  Intermediate-scale refers to the volume of qubits that they can connect and use, which as of today ranges from 50 to ~150 qubits.

Several types of qubits are in the market today. These innovative approaches to implementing quantum mechanics within a qubit are all part of the exploration of quantum computing to better understand which implementations will best deliver results for specific use cases.

Superconducting Qubits, or Transmons

These qubits, made from superconducting electrical circuits, are already in use in early stage NISC quantum computers made by Google, IBM, and others.

A superconductor is a material that changes from a normal state when it is cooled to a superconducting state where there is essentially no resistance to the flow of direct electrical current. This behavior makes superconductors an option for qubits in quantum computing.

Advantages: Superconducting qubits demonstrate fast operation times, meaning computations can be performed faster than on other qubits. This is important since quantum computations may have millions of operations that require speed. Another benefit is that superconducting qubits take advantage of existing printable circuit processes that are efficient and available. It’s the most straightforward approach to creating a quantum computer than with other, more innovation-driven, methods.

Disadvantages: Superconducting qubits quickly experience decoherence. They are very short-lived and therefore demand error correction techniques. Superconducting qubits are connected to the qubits next to them, limiting the size and depth of the circuit that can be run. They only operate in very cold environments, (below 100mK, or 0.1 degrees above absolute zero.)

Anyone who remembers chilled mainframe rooms will also remember the cost and complexity of building and maintaining such cold environments. Finally, due to fabrication, each superconducting qubit is different from others and therefore requires continuous calibration for operations.

Conclusion: 5 Questions to Decide Which Quantum Computer  

1.Things to Know About That Quantum Computer

2.Questions About Your Quantum Infrastructure

3.Which quantum computers are the best match for your problem?

4.How are you going to measure and test these systems?

5.How are you going to select the software/algorithms you need?

Thank you.