Redesigned Mobile Quantum Circuit Simulators (V2)

This article describes the revised version V2 of the mobile Quantum Circuit Simulator for n-qubit that I developed earlier.

▶️The new app name is nQsim_Aext.

🔴Addition of available quantum gates

The quantum gates shown in red below have been newly added.

[type1]

I, X, Y, Z, H, T, S, Td, Sd, √X , P(θ), RX(θ), RY(θ), RZ(θ)

 ("d" denotes "dagger", the angle(phase) θ should be given in radians, and π should be specified as "pi")

[type2]

Swap, QTF, QFTx, IQFT, IQFTx

 ("x" denotes Fourier transform without swap)

🔴Improvements to quantum circuit description format

・Comments (‘//’) can be placed anywhere on a line.

・Multiple quantum gates can be written on one line, separated by “;”.

・The name of the SWAP gate has been changed to Swap, and the argument “state” is no longer necessary.

・The newly added quantum Fourier transform has arguments given as follows:

[example] QFT, 0, 4 <- apply QFT to q0,q1,q2,q3

🔴Documentation screen setup

A separate screen with concise documentation. You can also jump to a blog with more detailed information.

🔴Phase Estimation built-in example

With the addition of QFT quantum gates, "Quantum Phase Estimation" has been added as a new built-in example. See the explanation below.

Here, a secret notation $$ is used that greatly reduces the amount of writing required. For example,

4$$P(2*pi/3),5,[2] -> P(2*pi/3),5,[2];P(2*pi/3),5,[2];P(2*pi/3),5,[2];P(2*pi/3),5,[2]

In this example, a phase shift gate P(2π/3) is used as an unitary operation. One of its eigenstates is |1>, so it is set to q5. Its phase 2π/3 = 120° is estimated by this quantum circuit. For this purpose, a phase kickback is applied to the five quantum bits q0, q1, q2, q3 and q4, which are the control bits. Finally, these quantum bits are measured after applying the inverse Fourier transform (IQFT).

As a result of the measurement, binary number "01011" (11 in decimal) was obtained with a probability of 68.4%. From this, the estimated phase = (360°/32)*11 = 123.75° is obtained. There is an error of about 3% from the correct answer of 120°. If the number of quantum bits used is increased, the accuracy should be further improved. 

🔴Two types of Bit-flip error correction

Bit-flip error correction incorporates two examples: "Bit-flip1" performs measurements to detect errors, then adds appropriate gates for error correction based on the results and runs again, whereas "Bit-flip2" automatically corrects errors without performing intermediate measurements.

[Note]

There is almost no syntax checking for quantum circuit descriptions. If you get abnormal results or the calculation does not proceed, please refer carefully to the built-in examples to resolve the issue.