We propose a normal form for single-qudit gates composed of Clifford and
T-gates for qudits of odd prime dimension
p≥5. We prove that any single-qudit Clifford+
T operator can be re-expressed in this normal form in polynomial time. We also provide strong numerical evidence that this normal form is unique. Assuming uniqueness, we are able to use this normal form to provide an algorithm for exact synthesis of any single-qudit Clifford+
T operator with minimal
T-count.
We present a complete set of
16 rewrite rules for multi-qudit Clifford circuits in all odd prime dimensions. Completeness means that any two Clifford circuits representing the same linear map can be rewritten into each other using these rules. Each rule involves at most three qudits and admits an intuitive interpretation. To establish completeness, we first work at the symplectic level, using the isomorphism between the symplectic group
Sp(2n,Zp) and the quotient of the Clifford group by the Pauli group. We construct a circuit normal form that captures the stabiliser tableau of a Clifford operator and is unique up to Pauli correction. Using this normal form, we derive a complete set of symplectic relations, which we then lift to Clifford relations by incorporating Pauli corrections. We also formally verify completeness in the Agda proof assistant.
We study single-qutrit gates composed of Clifford and
T gates, using the qutrit version of the
T gate proposed by Howard and Vala [M. Howard and J. Vala, Phys. Rev. A 86, 022316 (2012)]. We propose a normal form for single-qutrit gates analogous to the Matsumoto-Amano normal form for qubits. We prove that the normal form is optimal with respect to the number of
T gates used and that any string of qutrit Clifford+
T operators can be put into this normal form in polynomial time. We also prove that this form is unique and provide an algorithm for exact synthesis of any single-qutrit Clifford+
T operator.
Matsumoto and Amano (2008) showed that every single-qubit Clifford+T operator can be uniquely written of a particular form, which we call the Matsumoto-Amano normal form. In this mostly expository paper, we give a detailed and streamlined presentation of Matsumoto and Amano's results, simplifying some proofs along the way. We also point out some corollaries to Matsumoto and Amano's work, including an intrinsic characterization of the Clifford+T subgroup of SO(3), which also yields an efficient T-optimal exact single-qubit synthesis algorithm. Interestingly, this also gives an alternative proof of Kliuchnikov, Maslov, and Mosca's exact synthesis result for the Clifford+T subgroup of U(2).
In this paper we study single qutrit circuits consisting of words over the Clifford
+D cyclotomic gate set, where
D=diag(±ξa,±ξb,±ξc),
ξ is a primitive
9-th root of unity and
a,b,c are integers. We characterize classes of qutrit unit vectors
z with entries in
Z[ξ,χ1] based on the possibility of reducing their smallest denominator exponent (sde) with respect to
χ:=1−ξ, by acting an appropriate gate in Clifford
+D. We do this by studying the notion of `derivatives mod
3' of an arbitrary element of
Z[ξ] and using it to study the smallest denominator exponent of
HDz where
H is the qutrit Hadamard gate and
D. In addition, we reduce the problem of finding all unit vectors of a given sde to that of finding integral solutions of a positive definite quadratic form along with some additional constraints. As a consequence we prove that the Clifford
+D gates naturally arise as gates with sde
0 and
3 in the group
U(3,Z[ξ,χ1]) of
3×3 unitaries with entries in
Z[ξ,χ1]. We illustrate the general applicability of these methods to obtain an exact synthesis algorithm for Clifford
+R and recover the previous exact synthesis algorithm in \cite{kmm}. The framework developed to formulate qutrit gate synthesis for Clifford
+D extends to qudits of arbitrary prime power.
We present a complete set of rewrite rules for n-qutrit Clifford circuits where n is any non-negative integer.This is the first completeness result for any fragment of quantum circuits in odd prime dimensions.We first generalize Selinger's normal form for n-qubit Clifford circuits to the qutrit setting.Then, we present a rewrite system by which any Clifford circuit can be reduced to this normal form.We then simplify the rewrite rules in this procedure to a small natural set of rules, giving a clean presentation of the group of qutrit Clifford unitaries in terms of generators and relations.