The answer, up front
Quantum technology has three pillars, and each moves at its own pace. Sensing is the most mature in practice, computing gets the most attention but remains early, and communications is where executives most often get misled. For protecting data, government agencies favor post-quantum cryptography (PQC) over quantum key distribution (QKD) 1, 2, 3.
Last verified: Sep. 30, 2026.
The three pillars at a glance
| Pillar | What it does | Maturity | Main executive question |
|---|---|---|---|
| Sensing | Measures physical quantities with extreme sensitivity | Some devices mature, others in development | Where would better measurement help us? |
| Computing | Runs certain calculations classical machines struggle with | Early, noisy hardware | Where do we build skills and test problems? |
| Communications | Uses quantum effects to exchange keys or information | QKD is niche; agencies prefer PQC | How do we protect data from future decryption? |
Leaders who track only computing miss the other two. The sections below take each in turn.
Quantum sensing: better measurement
Quantum sensors use the sensitivity of quantum systems to measure magnetic fields, gravity, acceleration and time. NIST notes that sensors of this kind are not new: atomic clocks and atomic-spin magnetometers date back decades 5, 6.
Three examples show the range:
- Brain imaging. Room-temperature atomic magnetometers can be much smaller than older superconducting detectors. NIST reports a study in which one showed higher signal-to-noise than a traditional SQUID magnetoencephalography system, and researchers hope for more accessible monitoring for children 5.
- Navigation. Portable atomic magnetometers could measure Earth's magnetic field to support GPS-free navigation, and quantum accelerometers paired with an atomic clock could help a vessel track its position for long periods 5, 6.
- Gravimetry. Quantum gravimeters could help find mineral deposits, hidden voids, and groundwater changes 6.
Treat each claim as a capability under development. Test it against your own use case before you budget for it.
Quantum computing: most discussed, still early
Quantum computers use quantum effects to tackle certain calculations, such as simulation and some optimization problems, that classical machines handle poorly. Today's machines sit in what Preskill called the NISQ era: noisy devices of roughly 50 to 100 qubits, where gate noise limits circuit depth 4.
That description still frames the practical question. Near-term machines are useful for research and for exploring narrow problems. They do not yet justify betting a business plan on them.
ArcQubit guidance: build skills and a short list of candidate problems now, and keep spending proportionate.
Quantum communications: where the security claims need care
Quantum communications covers techniques that use quantum effects to exchange information. The best known is QKD, which lets two parties generate shared keys and detect some forms of eavesdropping.
QKD sounds like a direct answer to harvest-now-decrypt-later risk. Government cryptographic agencies disagree that it is a general answer.
- NSA: QKD has limitations and implementation challenges that make it impractical for National Security System operational networks. NSA views quantum-resistant cryptography as the better path 1.
- UK NCSC: QKD does not provide authentication. The NCSC calls PQC the best mitigation against quantum computers and says it will not support QKD for government or military applications 2.
- ANSSI, BSI and partners: QKD has significant functional limitations, is only suitable for niche use cases, and needs dedicated infrastructure. These agencies urge PQC instead 3.
QKD does not replace post-quantum cryptography. PQC is software that runs on existing systems and follows NIST standards. Read how in the NIST PQC standards guide.
The ANSSI paper adds that QKD research should continue 3. Watching the field is reasonable. Building a migration plan around it is not.
What this means for executives and the board
Three points matter most.
- The security risk is here now. Attackers can collect encrypted data today and decrypt it once a capable quantum computer exists. Our harvest-now-decrypt-later post explains how to test your data against that risk.
- Sensing and computing are opportunity questions. They reward curiosity and small pilots, not urgency.
- Communications is a procurement trap. A vendor pitch that presents QKD as a replacement for PQC conflicts with the agencies cited above.
Questions to ask your team this week
- Which of our data must stay confidential for 10 years or more?
- Do we have a current inventory of where we use public-key cryptography?
- Has anyone proposed QKD, and what problem would it solve that PQC does not?
- Which of our operations depend on precise measurement, navigation or timing that a quantum sensor could improve?
- Who owns our quantum strategy across all three pillars?
Common mistakes
- Treating quantum as one topic. The pillars have different owners, budgets and timelines.
- Buying QKD to avoid a PQC migration. Agencies do not support that trade.
- Waiting for error-corrected computers before acting. The security work starts before they arrive.
- Skipping the business case for sensing. Interesting physics is not a use case.
See quantum readiness vs. quantum maturity for a way to tell what to do now from what to watch.
How ArcQubit approaches it
This box describes ArcQubit's own services.
the AI & Quantum Consulting team advises executives and boards on where quantum technologies create advantage or risk, and supports quantum-powered analytics. For the security half, QuCode finds quantum-vulnerable cryptography in your environment, and QuTrust keeps the migration roadmap current. ArcQubit sells QuCode directly as fixed-scope work. Contact ArcQubit to start.