# Compressed quantum computation using the IBM Quantum Experience

## TL;DR

This paper demonstrates simulating a 1D Ising model's quantum phase transition on IBM's cloud quantum computer using compressed quantum computation, measuring magnetization on a small system with error assessment methods.

## Contribution

It introduces a method to simulate larger quantum systems using fewer qubits on cloud quantum computers, with validation techniques for error analysis.

## Key findings

- Successful simulation of a four-qubit Ising chain on two qubits
- Measurement of magnetization aligns with theoretical predictions
- Proposed validation circuits for error assessment in cloud quantum computing

## Abstract

The notion of compressed quantum computation is employed to simulate the Ising interaction of a 1D--chain consisting out of $n$ qubits using the universal IBM cloud quantum computer running on $\log(n)$ qubits. The external field parameter that controls the quantum phase transition of this model translates into particular settings of the quantum gates that generate the circuit. We measure the magnetization, which displays the quantum phase transition, on a two--qubit system, which simulates a four--qubit Ising chain, and show its agreement with the theoretical prediction within a certain error. We also discuss the relevant point of how to assess errors when using a cloud quantum computer. As a solution, we propose to use validating circuits, that is to run independent controlled quantum circuits of similar complexity to the circuit of interest.