4 votes

Can you decompose a 4-qubit Toffoli gate (CCCX) into basic gates without an ancillary state?

The seminal paper Barenco et al., Elementary gates for quantum computation is a great resource for decompositions of many quantum gates, including multi-control Toffoli gates, into elementary gates. (...
Norbert Schuch's user avatar
2 votes

Hello world program in Qiskit 1.0

I am not pretty sure about"Hello World" program as you stated. However, if you want to run a simple circuit on one of the backends that requires minimum time to be executed, then you can ...
physicino's user avatar
  • 111
2 votes
Accepted

Help finding mistake when modifying $T$ injection protocols

When applying the CNOT(1 $\rightarrow$ 2) you got confused in the last row. The $(1-\omega)|1\rangle$ flips the second qubit so $(\alpha+\beta)|0\rangle$ turns into $(\alpha+\beta)|1\rangle$ (and the ...
David Dentelski's user avatar
2 votes
Accepted

Why are qubits initialized to $|0\rangle$ in parametrized quantum circuits?

To be able to initialize a quantum computer with some initial state is one of DiVincenzo criteria of quantum computing. To start with all qubits in state $|0\rangle$ seems reasonable, as it is an ...
Martin Vesely's user avatar
1 vote

How to introduce non-linearity into a quantum circuit?

I would say that the only way to do anything "nonlinear" on a quantum computer is to make the Hilbert space "big enough" that the linear dynamics on that space are sufficient to ...
Cuhrazatee's user avatar
1 vote
Accepted

Simulating Large Quantum Systems with Single T-Gate in Qiskit: Memory Error Beyond Certain Qubit Threshold

On IBM Quantum platform, a universal simulator is limited by 32 qubits. There is also 64-qubit simulator Clifford+T which could be suitable for your problem. You can also run your circuit on 127-qubit ...
Martin Vesely's user avatar
1 vote

In what limit does the estimator sample variance converge to the Cramer-Rao bound?

The answer is the same as for the other question of yours: no, the efficiency is asymptotic in $\nu$ not in $\mu$. The MLE is not efficient (in general) for any finite finite number of observations. ...
glS's user avatar
  • 24.9k
1 vote

Getting rid of extra qubits without changing phase

Just apply $\text{CNOT}$ from the first qubit to every other qubit. Let $|\psi\rangle$ be the initial state. $$|\psi\rangle = \frac{1}{\sqrt{2}}|0000\rangle + \frac{e^{i\phi}}{\sqrt{2}}|1111\rangle\,.$...
FDGod's user avatar
  • 2,391
1 vote

Help finding mistake when modifying $T$ injection protocols

After the second $H\otimes H$ operator, once the mistake with the CNOT is corrected, the qubits should be in this state: $$\frac{1}{\sqrt{2}}\left(\alpha\left|00\right\rangle + \beta\omega\left|01\...
AG47's user avatar
  • 476
1 vote
Accepted

How do I get the unitary matrix of a circuit?

You can get back the matrix by using the save_unitary() method on the circuit after creating your circuit. Here is an example : ...
Lena's user avatar
  • 2,597
1 vote

How to Properly Run a Circuit with Qiskit on AWS Braket, AttributeError: 'AwsDevice' object has no attribute 'configuration' by Current Implementation

AWSBraketProvider is deprecated, and should be replaced by BraketProvider. After following fagd's answer and using BraketProvider, I am able to submit my jobs.
Chien Kai Ma's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible