Questions tagged [gate-synthesis]
For questions about finding (short) gate sequences to implement a specific unitary operation, for example decomposing a complicated multi-qubit gate into a sequence of basic gates. It might apply to optimizing circuits with respect to length or depth or finding gate sequences to implement an algorithm.
240 questions
3 votes
0 answers
126 views
How to implement $U|i\rangle=|2^i\rangle$ without ancilla qubits?
I want to implement a unitary operation $U$ on $n$ qubits, which performs the following mapping on computational basis states: $$U|i\rangle = |2^i\rangle,\quad \forall i \in [0, n-1]$$ When $i\geq n$, ...
0 votes
0 answers
49 views
Is this a correct DAG from parsing QASM?
Currently writing a QASM parser and wondering if this is the proper way to parse a program using a DAG (Deutsch's from QASMBench in this example). The output from Deutsch's would be: ...
1 vote
1 answer
66 views
Is there a more efficient/better way to prepare the History-State using poly(n)-depth circuit?
The paper mentions that the following state can be prepared efficiently (in terms of parameter $L$). (Page 7 of this paper) $$|{\eta}\rangle = \frac{1}{\sqrt{L+1}}\sum_{j=0}^{L} U_j\cdots U_1\Big(|{\...
3 votes
2 answers
80 views
Synthesis of single-qubit rotation in time $O(\log(1/\epsilon))$
Can a gate sequence approximating a given single-qubit rotation up to precision $\epsilon$ be compiled in time $O(\log(1/\epsilon))$ (i.e., time strictly logarithmic and not polylog)?
2 votes
1 answer
95 views
What is the circuit for $e^{-i \theta Z\otimes (X X + Y Y)}$?
I recently noticed that some quantum computers supply native gate $$iSWAP_{\theta} = e^{-i \theta (XX + YY)}.$$ I wonder, how do I build a circuit for $$e^{-i \theta Z\otimes(XX + YY)}$$ Is this one ...
1 vote
1 answer
184 views
Are there tools to generate fusion based (FBQC) gates
What I'm looking for is something that takes a standard gate (simple paulis for example) and give its fusion based (FBQC) equivalent; this would be two sets of pauli strings on n qubits : the first ...
2 votes
1 answer
127 views
does every quantum circuit have a "canonical form"
I'm reading through this recent survey paper and on page 18 it states that "every quantum circuit can be transformed into a canonical form : product of (clifford gate)* ($\pi/8$ pauli-product ...
2 votes
1 answer
107 views
does the standard form of a stabilizer code minimize the number of CX/CZ gates needed to encode it?
Given a stabilizer code, there are several ways to transform it to an equivalent code (same n,k,d). The "standard form" is one option and it seems to have lower CX and CZ gate count needed ...
7 votes
1 answer
243 views
Depth and Width Bounds for Controlled Unitaries in Quantum Circuits
Let $U$ be a unitary operator acting on $d$ qubits constructed by taking tensor products of single-qubit rotation gates. Let $C^nU$ denote a controlled-$U$ operation, where the control is implemented ...
1 vote
1 answer
189 views
Short way to create a good |T> state using Clifford+Toffoli+M
Clifford+Toffoli+M is a universal gate set. What's a cheap way to approximately (or exactly) get a T state using this gate set? I know that once I have a T state I can catalyze more very easily, but ...
1 vote
0 answers
92 views
Can an arbitrary angle Givens rotation be implemented with a single arbitrary angle 1-qubit rotation?
I know that a Givens rotation is the product of a $X\otimes X$ and a $Y\otimes Y$ rotation. Each Pauli string rotation can be reduced to a single qubit rotation (see Fig. 2 in [1] or Fig 12. in [2] ...
2 votes
0 answers
104 views
Procedure for constructing magic state gate injection gadgets
I have a quantum computer that cannot implement the gate $U$ by itself, and needs help in the form of a magic state $|U\rangle$ held in another register. Is there a general-purpose procedure for ...
1 vote
1 answer
305 views
Simple successor gate
I want to create a gate that, given a sequence of qbits that encode n, transforms that sequence in n+1, in other words the successor function. I managed to do it in qiskit by writing this: ...
1 vote
2 answers
303 views
Can I efficiently decompose this flexible unitary matrix into 1 and 2 qubit gates?
Consider the unitary matrix $A \in \mathbb{R}^{n^2\times n^2}$ which has only the first $n$ rows explicitly defined, with the remaining rows having some flexibility. $A$ can be written in block form ...
3 votes
1 answer
271 views
Is Controlled$(R_z(\theta))$ more expensive than Controlled$(Z^t)$ on the surface code?
There are (at least) two conventions for single-qubit, arbitrary-angle Z rotations in quantum computing, which I will call Rz(theta) and Z^t. $$ R_Z(\theta) = \exp(-i \theta Z/2) = \mathrm{diag}(e^{-i ...