A controlled-diffusion operator for Boolean oracles is designed as a new approach for Grover's algorithm to search for solutions for arbitrary logical structures of such oracles, since the Grover diffusion operator is not able to find correct solutions for some logical structures of Boolean oracles. We also show that the Phase oracles do not work sometimes correctly using the Grover diffusion operator. Our proposed controlled-diffusion operator relies on the states of output qubit, as the reflection of Boolean decisions from a Boolean oracle without relying on the phase kickback. We prove that on many examples of Boolean and Phase oracles the Grover diffusion operator is not working correctly. The oracles in these examples are constructed using different structures of POS, SOP, ESOP, CSP-SAT, and XOR-SAT. Our mathematical models and experiments prove that the proposed controlled-diffusion operator successfully searches for all solutions for all Boolean oracles regardless of their different logical structures.
A controlled-diffusion operator for Boolean oracles is designed as a new approach for Grover's algorithm to search for solutions for arbitrary logical structures of such oracles, since the Grover diffusion operator is not able to find correct solutions for some logical structures of Boolean oracles. We also show that the Phase oracles do not work sometimes correctly using the Grover diffusion operator. Our proposed controlled-diffusion operator relies on the states of output qubit, as the reflection of Boolean decisions from a Boolean oracle without relying on the phase kickback. We prove that on many examples of Boolean and Phase oracles the Grover diffusion operator is not working correctly. The oracles in these examples are constructed using different structures of POS, SOP, ESOP, CSP-SAT, and XOR-SAT. Our mathematical models and experiments prove that the proposed controlled-diffusion operator successfully searches for all solutions for all Boolean oracles regardless of their different logical structures.
The Grover controlled-diffuser (CUs) for quantum Boolean oracles (Uω) is introduced as a new approach for Grover’s algorithm [1-3], to search for all solutions for arbitrary logical structures of such oracles, since the standard Grover diffuser (Us) [1-3] is not able to find all correct solutions for some logical structures of Uω. This protocol constructs the quantum circuit of the CUs operator [4] of Grover's algorithm, which relies on the states of the output qubit (as the reflection of Boolean decisions from a Uω) without relying on the conventional phase kickback mechanism. The CUs operator successfully searches for all correct solutions for all Uω regardless of their different logical structures, such as POS, SOP, ESOP, CSP-SAT, XOR-SAT, just to name a few.
The Grover controlled-diffuser (CUs) for quantum Boolean oracles (Uω) is introduced as a new approach for Grover’s algorithm [1-3], to search for all solutions for arbitrary logical structures of such oracles, since the standard Grover diffuser (Us) is not able to find all correct solutions for some logical structures of Uω. This protocol constructs the quantum circuit of the CUs operator [4] of Grover's algorithm, which relies on the states of the output qubit (as the reflection of Boolean decisions from a Uω) without relying on the conventional phase kickback mechanism. The CUs operator successfully searches for all correct solutions for all Uω regardless of their different logical structures, such as POS, SOP, ESOP, CSP-SAT, XOR-SAT, just to name a few.
Lov K. Grover introduced, in 1996, Grover's algorithm as a quantum search algorithm to find all solutions for quantum oracles representing classical problems. My research observed that the Grover diffusion operator of Grover's algorithm gives wrong solutions when Boolean oracles are designed in some logical structures. Therefore, I invented the new "controlled-diffusion operator" for Boolean oracles as a new approach for Grover's algorithm that always correctly solves the problem of Grover's algorithm. Another important problem in quantum computing is designing reliable and cost-effective quantum gates using reversible binary logic. In classical logic design, the stage of logic design can be separated from the stage of mapping topological circuits to geometrical architecture. In contrast to classical logic design, the stages of quantum circuit design are not separable. For practical quantum applications, a quantum circuit is realized (transpiled) into the layout of a real quantum device. For a real quantum device, two factors affect the cost-effective transpilation: the utilization of supported (native) gates and the geometrical connectivity pattern of n neighboring physical qubits, where native gates ensure cost-effective transpilation and n ≥ 2. In this dissertation, I introduced two new approaches to leverage these two factors for real IBM quantum devices. The first approach initializes the uniform distribution for all qubits using IBM native √X gates, instead of using the conventional Hadamard gates, which are IBM non-native gates producing cost-expensive transpilation. The second approach geometrically constructs generic and cost-effective quantum gates using IBM native gates. In literature the Bloch sphere is used as a visualization tool for a quantum gate, which is initially designed using unitary matrices computations. In contrast, I introduced the Bloch sphere approach (BSA) as a "geometrical design tool" to design a quantum gate using the Bloch sphere, which leads to fewer unitary matrices computations. I employed the BSA to design various generic and cost-effective quantum gates and libraries based on the layouts of IBM quantum devices. Using the BSA, I invented two quantum libraries to investigate the trade-off between scalability and reliability, for the purpose of how the input qubits of a quantum gate are routed into the layout of an IBM quantum device and how many ancilla qubits are utilized. Experimentally, for the same layout of an IBM quantum device, I prove that the transpiled quantum circuits of oracles utilizing my two approaches always have lower quantum costs and shorter depths than those of the transpiled quantum
Grover's search algorithm drives a quantum system from an initial state $|s\ensuremath{\rangle}$ to a desired final state $|t\ensuremath{\rangle}$ by using selective phase inversions of these two states. Earlier, we studied a generalization of Grover's algorithm that relaxes the assumption of the efficient implementation of Is, the selective phase inversion of the initial state, also known as a diffusion operator. This assumption is known to become a serious handicap in cases of physical interest. Our general search algorithm works with almost any diffusion operator Ds with the only restriction of having $|s\ensuremath{\rangle}$ as one of its eigenstates. The price that we pay for using any operator is an increase in the number of oracle queries by a factor of O(B), where B is a characteristic of the eigenspectrum of Ds and can be large in some situations. Here we show that by using a quantum Fourier transform, we can regain the optimal query complexity of Grover's algorithm without losing the freedom of using any diffusion operator for quantum searching. However, the total number of operators required by the algorithm is still O(B) times more than that of Grover's algorithm. So our algorithm offers an advantage only if the oracle operator is computationally more expensive than the diffusion operator, which is true in most search problems.
Quantum search is among the most important algorithms in quantum computing. At its core is quantum amplitude amplification, a technique that achieves a quadratic speedup over classical search by combining two global reflections: the oracle, which marks the target, and the diffusion operator, which reflects about the initial state. We show that this speedup can be preserved when the oracle is the only global operator, with all other operations acting locally on non-overlapping partitions of the search register. We present a recursive construction that, when the initial and target states both decompose as tensor products over these chosen partitions, admits an exact closed-form solution for the algorithm's dynamics. This is enabled by an intriguing degeneracy in the principal angles between successive reflections, which collapse to just two distinct values governed by a single recursively defined angle.
Applied to unstructured search, a problem that naturally satisfies the tensor decomposition, the approach retains the O(N) oracle complexity of Grover search when each partition contains at least log2(log2N) qubits. On an 18-qubit search problem, partitioning into two stages reduces the non-oracle circuit depth by as much as 51%-96% relative to Grover, requiring up to 9% additional oracle calls. For larger problem sizes this oracle overhead rapidly diminishes, and valuable depth reductions persist when the oracle circuit is substantially deeper than the diffusion operator. More broadly, these results show that a global diffusion operator is not necessary to achieve the quadratic speedup in quantum search, offering a new perspective on this foundational algorithm. Moreover, the scalar reduction at the heart of our analysis inspires and motivates new directions and innovations in quantum algorithm design and evaluation.
Grover's search algorithm is one of the well-studied quantum computing algorithms, which plays a key role in many applications such as graph coloring, triangle finding, Boolean satisfiability. Although there are many works on circuit synthesis for Grover's algorithm in the binary quantum domain, only a few exist for the ternary version of the algorithm. In this paper, we first propose a new ternary superposition operator and utilize it to synthesize a ternary quantum logic circuit for Grover's algorithm. Our proposed circuits for a ternary oracle and the ternary Grover's diffusion operator require 4 and 6 gate levels respectively per iteration, and for the ternary oracle 1 ancilla qutrit. To the best of our knowledge, this is the first circuit for the Grover's diffusion operator using ternary gates. Finally, we use these two circuits to present a ternary quantum circuit for the vertex coloring problem. The oracle circuit for this problem has smaller gate count compared to existing solutions.