Scaling quantum systems

Scaling quantum systems

In order to increase the computational power of quantum computing systems, improvements are needed along two dimensions. One is qubit count; the more qubits you have, the more states can in principle be manipulated and stored. The second is to achieve lower error rates. We need to be able to manipulate the qubit states accurately and perform sequential operations that provide answers, not noise.

Combining these two concepts, we can create a single measure of a quantum computer’s power called quantum volume. Quantum volume measures the relationship between number and quality of qubits, circuit connectivity, and error rates of operations. Building larger systems with lower error rates will lead to discovering the first instances of quantum advantage, or applications where quantum computers can offer a computational advantage for solving real problems.

Quantum Computation

Quantum Computation

How do quantum systems use quantum properties to compute?This question can be split into two parts:

• How are algorithms developed for the quantum computers available today?
• How do people create algorithms for future “fault tolerant” quantum systems that are still theoretical?

Many algorithms for near-term quantum hardware require you to find the “best” solution from among many possible solutions, such as finding the lowest energy state of a molecule among various possible molecular bond lengths. For each possible bond length, you represent parts of the energy on a quantum processor, and then measure the energy directly. Trying various solutions eventually leads to the bond length with to the lowest energy state, which represents the equilibrium molecular configuration. More information can be found here.

Algorithms for the kinds of quantum systems we hope to have in the future, called fault tolerant universal quantum computers, were among the first to be developed in the field. This includes some of the most well known examples: Shor’s factorization algorithm and Grover’s algorithm for unstructured search. While near-term algorithms involve relatively few qubits and operations, and errors can be compensated by running the algorithm many times to get an average value, fault-tolerant algorithms require extremely long gate sequences and high gate fidelities to perform well. The quantum hardware needed for fault-tolerant algorithms is still being developed; however, they demonstrate that certain quantum algorithms can outperform their classical counterparts, given the right quantum system.

Komentarji

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What is quantum computing

What is quantum computing?

Over 50 years of advances in mathematics, materials science, and computer science have transformed quantum computing from theory to reality. Today, real quantum computers can be accessed through the cloud, and many thousands of people have used them to learn, conduct research, and tackle new problems.

Quantum computers could one day provide breakthroughs in many disciplines, including materials and drug discovery, the optimization of complex systems, and artificial intelligence. But to realize those breakthroughs, and to make quantum computers widely useable and accessible, we need to reimagine information processing and the machines that do it.

https://www.research.ibm.com/ibm-q/learn/what-is-quantum-computing/