Quantum Machine Achieves 120-Qubit Entanglement, Enabling Larger Schrödinger Cat State Preparation

Entanglement, a fundamental property of quantum mechanics, underpins the potential of quantum computing, and creating highly entangled systems serves as a crucial test of hardware and control. Ali Javadi-Abhari, Simon Martiel, and Alireza Seif, all from IBM Quantum, alongside colleagues, now report the creation of the largest entangled state to date, involving an impressive 120 quantum bits. The team achieves this breakthrough by combining advanced compilation techniques, efficient error detection, and a novel method of temporary uncomputation, allowing them to overcome the inherent challenges in preparing such delicate states. Measuring a fidelity of 0. 56, this achievement represents a significant step forward in building more powerful and reliable quantum computers, demonstrating the potential to scale up quantum systems beyond previous limitations and paving the way for more complex quantum algorithms.

Qubit GHZ State Achieves High Fidelity

Scientists have demonstrated entanglement in 120 qubits, a significant step forward in quantum computing. Entanglement, a fundamental quantum phenomenon, is crucial for developing powerful quantum algorithms. The ability to reliably entangle many qubits serves as a key measure of the quality of quantum hardware and control systems. Greenberger, Horne, and Zeilinger (GHZ) states, a specific type of entangled state, are particularly sensitive to noise, making them ideal for assessing the performance of quantum systems. This work reports the creation and verification of a GHZ state involving 120 qubits, representing a major advance in both the scale and fidelity of multi-qubit entanglement.

Researchers carefully calibrated a sequence of microwave pulses to induce entanglement across the qubits, simultaneously implementing sophisticated error mitigation techniques to minimize the effects of noise. The resulting GHZ state exhibits a measured fidelity exceeding previously reported values, confirming the effectiveness of their approach and opening the door to more complex quantum computations. GHZ states are valuable for assessing quantum systems because they are relatively easy to verify, yet difficult to prepare due to their sensitivity to noise. The team achieved this through a combination of optimized control sequences, low-overhead error detection, and a technique called temporary uncomputation.

An automated compiler maximizes error detection during state preparation, accommodating variations in qubit connectivity and error rates. Measurements confirm a fidelity of 0. 56 with a post-selection rate of 28 percent.

Twenty Qubit GHZ State Achieves High Fidelity

Researchers successfully created and verified a high-fidelity entangled state, specifically a 20-qubit Greenberger-Horne-Zeilinger (GHZ) state. This is a challenging task because quantum states are fragile and susceptible to noise. The goal was to generate a GHZ state, characterize its fidelity, and develop accurate methods for fidelity estimation. A GHZ state is a highly entangled state where all qubits are correlated. Fidelity is a crucial metric in quantum computing, measuring how close the created state is to the ideal GHZ state.

Researchers used a technique called the stabilizer formalism to characterize the quantum state, allowing them to reconstruct the state from a set of measurements. Dynamical decoupling, a technique to suppress noise and extend qubit coherence, was also employed. The researchers used stabilizer operators to measure the properties of the GHZ state, calculating expectation values to estimate the state’s fidelity. They also addressed the impact of readout errors, which can affect the accuracy of measurements. The experiment was performed on a 20-qubit superconducting device, and the timing of pulses for dynamical decoupling and gate operations was carefully controlled. The results demonstrate the ability to create a relatively high-fidelity 20-qubit GHZ state, a significant achievement in quantum computing. The validated methods for accurate fidelity estimation are crucial for benchmarking quantum devices and comparing different quantum algorithms.
Qubit Entanglement and Fidelity Certification

Scientists have successfully created and verified a large entangled state consisting of 120 qubits, representing a significant advance in quantum information science. This achievement surpasses previous demonstrations of multi-qubit entanglement and establishes a new benchmark for the fidelity of quantum systems. The team employed optimized control sequences, low-overhead error detection, and a technique called temporary uncomputation to prepare the complex state, demonstrating precise control over a substantial number of qubits. Measurements confirm a fidelity of 0. 56 for the generated entangled state, achieved with a post-selection rate of 28 percent.

Researchers utilized multiple independent methods to certify the fidelity of the state, confirming the reliability of their results and the robustness of the entanglement. The work highlights the potential for scaling up quantum systems and performing increasingly complex quantum computations. While a significant step forward, the achieved fidelity remains below the threshold required for fault-tolerant quantum computation, and future research will focus on improving fidelity and mitigating the effects of noise.