Quantum Circuit Loading Classical Data via Ancilla Entanglement
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Solution Overview
Problem
Current methods for entangling qubits in quantum computers have high computational complexity, making it expensive to achieve the exponential speedup benefits of quantum computation, as existing generic methods require large gate depths that negate the advantages of quantum computation.
Innovation Solution
A quantum circuit that deterministically loads N classical bits into an entangled quantum state using ancilla qubits, with a gate depth of order O(n), allowing for efficient entanglement and disentanglement in a single time slice, enabling optimal Log2(N) gate depth for quantum algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If generic methods for entangling qubits are used, then entanglement is achieved, but gate depth becomes large which negates quantum computation advantages
Solution Approach 1:
The patent applies preliminary action by pre-preparing entangled ancilla qubit states before the main computational process. The system prepares ancilla qubits in specific entangled states (such as Bell states or GHZ states) in advance, which are then used to entangle with data qubits efficiently. This pre-preparation eliminates the need for complex real-time entangling operations during computation, thereby reducing gate depth while maintaining entanglement quality.
Solution Approach 2:
The patent uses ancilla qubits as intermediary elements to facilitate entanglement between data qubits. Instead of directly entangling data qubits through complex multi-qubit gates, the system introduces ancilla qubits that are first prepared in entangled states and then interact with data qubits through simpler interaction gates. This intermediary approach reduces the overall gate depth required for entanglement while preserving the desired quantum correlations.
2Productivity
If ancilla qubits are used for entanglement, then loading efficiency improves, but qubit resources are consumed
Solution Approach 1:
The patent implements discarding and recovering by using ancilla qubits temporarily for the entanglement process and then disentangling them from the computational system after their purpose is fulfilled. The ancilla qubits are prepared, used to establish entanglement with data qubits through controlled operations, and then disentangled through reverse operations. This allows the ancilla qubits to be reset and reused for subsequent operations, effectively managing qubit resources while maintaining high data loading efficiency.
3Reliability
If high gate depth is used for entanglement, then entanglement is achieved, but computational time increases
Solution Approach 1:
By preparing ancilla qubits in entangled states before the main computation, the system eliminates the need for deep entangling gate sequences during the computational process. The preliminary preparation of ancilla states (such as applying Hadamard gates followed by controlled-NOT gates to create Bell states) occurs outside the critical computational path, thereby reducing the gate depth and computational time required for entanglement while maintaining high fidelity.
Solution Approach 2:
The patent segments the entanglement process into distinct phases: ancilla preparation phase, interaction phase, and disentangling phase. Each phase uses optimized gate sequences tailored to its specific requirements. The ancilla preparation phase uses shallow circuits to create entangled states, the interaction phase uses controlled operations that preserve entanglement fidelity, and the disentangling phase efficiently separates ancilla from computational qubits. This segmentation reduces overall computational time while maintaining entanglement quality.
Data Source
AI summary
Quantum circuits and methods load N=2n classical bits into an entangled quantum output state using a gate depth of order O(n). Loading is accomplished by dividing the 2n input bits into data words and entangling these data words using ancilla qubits. The output of the circuit consists of one data word and one or several index qubits, drawn from the ancilla, to select between the input data words. Entanglement of the data words is performed in a single time slice (i.e. with a gate depth of 1), while the number of sequential gates needed to produce the appropriate pre-entanglement quantum state in the ancilla, and to disentangle the non-output ancilla, has the desired order O(n). Also disclosed is a circuit for disentangling qubits used to store non-output data words during processing.