*Ph.D. students from Swiss Federal Institute of Technology made some noise in the science community when they successfully simulated a 45-qubit quantum circuit–the largest ever simulation of a quantum computer to date.*

The two students, **Thomas Häner** and **Damien Steiger** performed the computations at the **National Energy Research Scientific Computing Center (NERSC)**. This DOE Office of Science User Facility exists at the U.S. Department of Energy’s **Lawrence Berkeley National Laboratory**.

As it stands, researchers have been studying **quantum computing** for decades. It all began when **Paul Benioff** first applied quantum theory to computers in 1981.

Modern day computers use digital computing which requires all data to be encoded in binary digits (bits). On the other hand, Benioff’s quantum computer or **Quantum Turing machine** is a theoretical model which requires the use of quantum bits in its computation.

Unlike the regular bit which can only be 1 or 0, a **quantum bit** or **qubit** can be in superposition. This is a state which allows it to hold more information. A quantum bit can contain a combination of 2 or more bits(1 or 0) by using superdense coding. The superposition state of qubits will allow a quantum computer to work on a million computations at once. A regular desktop computer can only work on one.

As a result, modern researchers like Häner and Steiger are pushing the limits of our generation’s most advanced supercomputers to develop future quantum computers. Using the fastest computing machines help these experts discover quantum computing breakthroughs. These will be useful in revolutionizing material science, machine learning, quantum chemistry, and cryptography.

## The Largest Quantum Device Simulating a 45-Qubit Circuit

Using Knights Landing-based **Cori II** machine at Lawrence Berkeley National Laboratory, Häner and Steiger succeeded in simulating a **45-qubit circuit**–the largest quantum device to date.

Cori II is NERCS’ newest supercomputer that has 9,304 compute nodes, each one outfitted with one 68-core Intel “Knights Landing” Xeon Phi 7250 processor, linked with the Cray Aries interconnect. The machine has a total peak performance of 29.1 petaflops and 1 PB of aggregate memory. For their simulation, Häner and Steiger only used 8,192 nodes and 0.5PB of memory which enabled them to achieve an average of 0.428 petaflops.

The first in #QuantumComputing. Students simulate a 45-qubit quantum circuit!Click To TweetBased on their research paper, Häner and Steiger followed Google’s proposal of using low-depth random quantum circuits simulation to demonstrate quantum supremacy. On their paper, the duo said:

*“The execution of low-depth random quantum circuits is not scientifically useful on its own but running such circuits is of great use to calibrate, validate, and benchmark near-term quantum devices.”*

Aside from 45-qubit, the duo was also able to simulate 30-, 36-, and 42-qubit quantum circuits. Moving forward, both Häner and Steiger expressed their determination to perform more quantum circuit simulations in the future. The two researchers are hoping to use solid-state drives to store larger wave functions that will enable them to simulate more qubits.

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