Quantum Volume Explained: A System-Level Performance Metric
Describe Quantum Volume.
IBM created Quantum Volume to measure quantum computers' true processing capacity. Unlike qubit counts, this metric considers hardware connections, error rates, and software compiler efficiency to assess performance. Finding the largest square circuit a machine can continuously operate yields an exponential number.
The Heavy Output Generation test ensures a device produces useful results rather than random noise. Despite application-specific workload constraints, it is a key industry benchmark for evaluating quantum computers' computational power. The paper stresses that hardware quality and durability, not scale, drive innovation.
Why Quantum Volume is the New Standard for Supercomputing Power in the Quantum Space Race Early in the quantum revolution, the industry sought qubit count. Tech businesses talked about 50, 72, or 100 qubit systems as if they were the only success factor. But as the field evolves in 2026, experts have found that outstanding performance doesn't always require many qubits.
If qubits are “noisy,” error-prone, or poorly linked, they cannot perform complex instructions. This revelation encouraged the industry to adopt Quantum Volume (QV), a more complete performance measure.
Beyond the Data: Orchestra Comparison
Professionals often utilize music to show why raw qubit figures are misleading. If qubit count matches the number of musicians on stage, a group can perform a difficult symphony without mistakes.
Ten world-class violinists are better than 100 non-players. Quantum volume considers qubit quality, gate fidelity, and coherence time.
Quantum Volume formula
Quantum Volume, a single benchmark figure representing actual capabilities, was introduced by IBM. It is measured using a “square” random quantum circuit with equal qubits (width) and operational steps (depth).
QV = 2k
Where k is the greatest number of qubits that may complete a square circuit, the simple yet effective formula is utilized.
To pass a test, the quantum computer must produce “heavy” outputs with a probability at least two-thirds higher than random guessing. A machine with a k-value of 10 maintaining a 10x10 circuit but failing at 11x11 has a Quantum Volume of 210, or 1,024.
How to Determine High Score?
High Quantum Volume is system-level, not hardware-level. Several aspects must work well together to boost the score:
Gate Fidelity: High error rates quickly impair calculations as the circuit deepens.
Connectivity is how easily qubits can "talk" across the semiconductor. Systems having “all-to-all” connectivity, such trapped-ion systems, perform better because they do not require additional “SWAP gates” that create errors.
Compiler efficiency depends on software stack. Intelligent compilers can enhance hardware performance by optimizing code for fewer steps.
Record and Competition Scene 2026
The quest for the largest Quantum Volume has become a high-stakes “space race” between technologies.
Trapped-ion systems lead this category. The company Quantinuum established a record of over 33.5 million quantum volumes in early 2026. Their H-Series systems, which reached 225 in September 2025, break records.
In the meantime, IBM advances superconducting technology. Their Heron r3 “Pittsburgh” system had 211 (2,048) QV in August 2025. Although easier to grow to huge qubit counts, superconducting devices often have more connectivity difficulties than trapped-ion devices.
Classical Simulation “Wall”
Quantum volume is approaching a fundamental limit despite its utilization. To validate a QV score, a traditional supercomputer must reproduce the circuit to verify the quantum machine's response.
After 50 qubits, ordinary computers cannot keep up with the simulation. The “proof” of scores for massive systems is nearly impossible. Layer Fidelity and CLOPS (Circuit Layer Operations Per Second) are being prioritized for the next generation of 1,000+ qubit CPUs.
The Future of Benchmarking
Although flawed, it uses fake random circuits instead of application workloads. Quantum Volume remains the most reliable indicator of progress in the NISQ era. Engineers are encouraged to build balanced machines rather than huge ones and loud systems are penalized.
Fault-tolerant logical qubits will modify power measurement. For now, how “smart” a quantum computer is depends on its volume, not its qubit count.