The Quantum Computer Security Risks You Likely Haven’t Heard About

You’ve almost certainly heard about the security issues that will arise when quantum computers are able to decrypt VPNs, data at rest, and most other forms of secure transmission and storage of data. While these issues get plenty of attention, there are other quantum security risks that could be even more significant.

Now is the time to go into something rarely talked about, but perhaps the most important topic, the inherent risk of quantum computer design.

Inherent Security Flaws in Quantum Computing Hardware

The best guide for technology and security professionals on this topic is the recently published IEEE “Primer on Security of Quantum Computing Hardware” (Volume 113, Issue 7, Nov 2025). The authors call for engineers to raise awareness of quantum computer security flaws because “despite the strategic significance of quantum computing and its potential to process sensitive information, its security and privacy concerns remain underexplored.” It gives details on the following inherent security risks that we must find ways to mitigate.

Quantum Crosstalk: How Qubits Can Leak Data Between Users

You are probably familiar with the term “crosstalk” from when you studied for your first technology certifications. If we put two wires close together, signals from one wire will bleed into the other, opening up the possibility of snooping or interference. We mitigate crosstalk by twisting the cable (twisted pair, for example) or shielding the cable (fiber).

Crosstalk in quantum computing comes from unwanted entanglement. Unwanted entanglement is not pineapple on all the pizza at a lunch-n-learn,* but rather, the linking of subatomic particles. Entanglement is at the heart of all quantum computers and is what the quantum qubits use to perform the calculations.

Why Qubits Create a New Attack Surface

Quantum computer qubits are “the big deal” in making quantum computers actually viable. The first device with 200-400 low-error qubits will be the world’s first useful quantum computer.**

So what is the crosstalk “flaw?” The security problem is that if more than one program or user accesses a qubit at the same time, they will be able to ‘see’ each other’s data and calculations. Considering the expense and rarity of such computers for the foreseeable future, it is unlikely that allowing only a single program to run at a time will be economically feasible. The ‘spy’ program could even communicate the stolen information out of the quantum computer without the knowledge of its operators or external security controls.

Can Quantum Computer Architecture Prevent Crosstalk?

How would we fix the crosstalk problem? Other than single-use at a time applications, stopping crosstalk would have to be designed into the qubit architecture. According to the IEEE, there does not appear to be any currently published designs or even research into doing this. Much like the problems with AI security, we might have to rely on standards or laws to encourage manufacturers to design these controls into their qubits.

The Lack of End-to-End Security in Quantum Computing Systems

Currently, quantum computing infrastructures are proprietary, and the software is created by third parties. This makes security controls, and research into creating them, almost impossible without external oversight. We have seen this problem before, but even AI is not on the scale of quantum computing. At the circuit level, techniques like information encoding must be built into the architecture and at the management level, there must be standards that allow controls to be implemented.

Any data entered into or produced by a current quantum computer must be considered and treated as exposed data. This means that health data, intellectual property data, personally identifiable data and the like must be kept out of quantum systems by law and policy until these issues are mitigated.

Excitement Without Oversight Creates Systemic Risk

The rush to produce viable quantum computers is exciting and a high priority for many organizations and countries. When seeking investments, many of the companies working on these technologies are touting health discoveries and benefits to society.

Without knowledgeable oversight and control over the information exposed to quantum systems, any benefits to society could be overshadowed by negative consequences. The time to start considering these issues is now.

Previous related articles:

Why quantum communications might make VPNs and VPN decryption irrelevant (https://blog.cadre.net/did-we-miss-chinas-quantum-sputnik)

Ridiculous VPN laws that do harm and no good (https://blog.cadre.net/update-michigan-law-banning-vpns-and-post-quantum-vpn-encryption)

Post-quantum encryption (https://blog.cadre.net/the-truth-about-vpns-and-the-rise-of-quantum-decryption).

*Actually, I like pineapple on pizza but this was the best example I could think of, and is inspired by an actual event.

** The phrase useful in this context means a quantum computer able to outperform a classical computer.

Sources:

Swaroop Ghosh, Suryansh Upadhyay, Abdullah Ash Saki. Proceedings of the IEEE, 2025; 113 (7): 640 DOI: 10.1109/JPROC.2025.3630989

Penn State. "Quantum computer security flaws." ScienceDaily, 20 January 2026.

Progress in Algorithms Makes Small, Noisy Quantum Computers Viable, ScienceDaily /releases/2021/08/210813100316

Notice:

AI did not generate this article. In fact, this article was drafted on a 1983 Apple LISA computer, which introduced the most profound advancement in personal computer history…

No part of this material may be used or reproduced in any manner for the purpose of training artificial intelligence.