This paper investigates the synthesis of quantum networks built to realize ternary switching circuits in the absence of ancilla bits. The results we established are twofold. The first shows that ternary Swap, ternary Not and ternary Toffoli gates are universal for the realization of arbitrary
n×n ternary quantum switching networks without ancilla bits. The second result proves that all
n×n quantum ternary networks can be generated by Not, Controlled-Not, Multiply-Two, and Toffoli gates. Our approach is constructive. key words: ternary quantum logic synthesis, quantum circuit optimization, group theory.
In this paper, we investigate the synthesis of ternary reversible circuits in the absence of ancilla bits. We demonstrated that 2-qudit ternary Swap, NOT and 1-controlled-NOT gates are universal for realization of arbitrary ternary n-qudit reversible circuits without ancilla qudits, and all even ternary n-qudit reversible circuits can be constructed by ternary NOT and ternary 1-controlled-NOT gates without ancilla qudits. The realization approach is constructive. This result is significantly different from the binary case.
Abstract. This paper presents an important result addressing a fundamental question in synthesizing binary reversible logic circuits for quantum computation. We show that any even-reversible-circuit of n (n>3) qubits can be realized using NOT gate and Toffoli gate (‘2’-Controlled-Not gate), where the numbers of Toffoli and NOT gates required in the realization are bounded by (n+ ⌊ n 3 ⌋)(3×22n−3 −2 n+2)and4n(n+ ⌊ n 3 ⌋)2n, respectively. A provable constructive synthesis algorithm is derived. The time complexity of the algorithm is 10 3 n2 · 2 n. Our algorithm is exponentially lower than breadth-first search based synthesis algorithms with respect to space and time complexities. 1
This paper presents a constructive synthesis algorithm for any n-qubit reversible function. Given any n-qubit reversible function, there are N distinct input patterns different from their corresponding outputs, where N les 2n, and the other (2n- N) input patterns will be the same as their outputs. We show that this circuit can be synthesized by at most 2nldrN '(n - 1)'-CNOT gates and 4n2ldr N NOT gates. The time complexity of our algorithm has asymptotic upper bound O(n ldr 4n). The space complexity of our synthesis algorithm is also O(n ldr 2n). The computational complexity of our synthesis algorithm is exponentially lower than the complexity of breadth-first search based synthesis algorithm.
Circuit synthesis of multi-controlled gates is crucial for qudit (
d-level) quantum computing. This paper presents efficient synthesis schemes that reduce the elementary gate count for multi-controlled single-qudit gates. For synthesizing general
(n−1)-controlled unitaries on
n qudits, we reduce the controlled-increment (CINC) and generalized controlled-
X (GCX) gate counts to
O(n2), improving upon existing
O(n2+log2d) CINC and
O(n3) GCX bounds. For
(n−1)-controlled special unitaries, this complexity is further reduced to
O(n). Furthermore, we present a method for approximately synthesizing multi-controlled unitary gates with a linear complexity in the number of control qudits. By utilizing the proposed circuit, we present qudit-based circuit constructions for isometries and quantum channels from
n to
m qudits. Moreover, for the first time, we present a circuit synthesis scheme for single-controlled gates using SUM gates and single-qudit gates when
d is prime. This enables all CINC-based circuits for various quantum operations to be converted into SUM-gate circuits while preserving the same asymptotic complexity. Finally, we establish a theoretical lower bound on the number of SUM and CINC gates required to synthesize general
n-qudit unitaries.
Reversible or information-lossless circuits have applications in digital signal processing, communication, computer graphics, and cryptography. They are also a fundamental requirement in the emerging field of quantum computation. We investigate the synthesis of reversible circuits that employ a minimum number of gates and contain no redundant input-output line-pairs (temporary storage channels). We prove constructively that every even permutation can be implemented without temporary storage using NOT, CNOT, and TOFFOLI gates. We describe an algorithm for the synthesis of optimal circuits and study the reversible functions on three wires, reporting the distribution of circuit sizes. We also study canonical circuit decompositions where gates of the same kind are grouped together. Finally, in an application important to quantum computing, we synthesize oracle circuits for Grover's search algorithm, and show a significant improvement over a previously proposed synthesis algorithm.