This article is part of the Quantum Snake Oil Dictionary — a series examining terms used in quantum technology marketing. The series is divided into Red Flag Terms (terms with no established technical meaning that almost always signal hype or fraud) and Misused Terms (legitimate concepts routinely stripped of context in marketing). This entry is a Misused Term.
A note before we begin. This article examines the term “simulated quantum entanglement” as it appears in security product marketing. I am not referring to any specific company, product, or individual. The term has been brought to my attention by readers and colleagues who encountered it in vendor pitches. My analysis is purely technical: does the concept make sense on its own terms?
It is possible that a product using this language is built on legitimate technology with an overzealous marketing department. It is also possible that future developments will give this term a clearly defined, defensible meaning. As of today, however, here is my assessment.
Quantum entanglement is a physical phenomenon in which two or more particles share a quantum state such that measuring one particle instantaneously constrains the possible outcomes of measuring the other, regardless of the distance between them. Einstein famously called it “spooky action at a distance,” and it troubled him precisely because it seemed to violate the principle that physical effects cannot travel faster than light.
The critical insight came in 1964, when physicist John Bell proved mathematically that entangled particles produce correlations that are impossible to replicate using any classical system operating with local variables. This is not a conjecture or an engineering limitation. It is a theorem with experimental confirmation. Experiments testing Bell inequalities have been conducted thousands of times, including loophole-free versions (Hensen et al. 2015, Giustina et al. 2015, Shalm et al. 2015). The result is always the same: quantum correlations exceed what any classical system can produce.
This is what makes entanglement useful for security. In entanglement-based quantum key distribution (QKD) protocols like E91 and BBM92, two parties share entangled photon pairs and use Bell inequality violations to verify that no eavesdropper has intercepted or substituted the quantum states. The security guarantee comes directly from the non-classical nature of the correlations. If the correlations could be faked classically, the security proof would collapse.
This is where the term “simulated quantum entanglement” runs into a wall of physics.
Bell’s theorem tells us that entanglement produces correlations that violate a specific mathematical bound (the Bell inequality, or more precisely the CHSH inequality). Classical systems, by definition, cannot violate this bound. A classical simulation of entanglement can mimic some statistical features of entangled states, but it cannot reproduce the Bell-violating correlations that are the entire basis of entanglement-based security.
To put this more concretely: if you could simulate quantum entanglement on a classical chip and get the same security properties, you would have disproved Bell’s theorem. You would have overturned one of the most experimentally verified results in the history of physics. That would be worth considerably more than a product launch.
The academic literature on classical simulation of entanglement actually confirms this limitation. Cerf, Gisin, Massar, and Popescu have published extensively on what it takes to classically simulate entangled correlations, and they’ve shown that even simulating a single entangled pair requires at least one bit of classical communication between the parties. This is a fundamental resource cost, and it means the simulation cannot be used as a drop-in replacement for entanglement in a security protocol, because the required classical communication channel reintroduces exactly the vulnerability that entanglement-based security is designed to eliminate.
There is also a body of work in classical optics on “classical entanglement” (sometimes called “non-separability”), where classical light beams exhibit correlations between different degrees of freedom (such as polarization and spatial mode). This is real physics, but the correlations are local and do not violate Bell inequalities. They have no application to cryptographic security.
Any product claiming security benefits from “simulated quantum entanglement” on classical hardware faces a simple logical test: if the simulation runs on classical hardware and does not use actual quantum states, it cannot produce Bell-violating correlations. If it cannot produce Bell-violating correlations, it cannot provide entanglement-based security. The term becomes a contradiction.
What the product might actually be doing could still be legitimate. It might be running a classical encryption algorithm, possibly a good one. It might be using a clever key exchange protocol. It might be implementing standard post-quantum cryptography. Any of those would have value. But calling it “simulated quantum entanglement” does not make it any of those things, and it does not confer any security property derived from quantum physics.
If a vendor uses the term “simulated quantum entanglement,” here are the questions I would ask:
“Does your system produce correlations that violate a Bell inequality?” If the answer is no (and on classical hardware, it must be no), then the system does not replicate the security-relevant property of entanglement. Ask what security property the system does provide, and on what mathematical basis.
“What specific cryptographic algorithm does your product implement?” Any credible security product can name its algorithm. If the answer is a proprietary, unpublished algorithm, that is a separate and significant red flag. See why proprietary algorithms are dangerous and why NIST’s public standardization process exists.
“Has your algorithm been submitted to any public cryptanalysis process, such as NIST’s post-quantum standardization?” Cryptographic algorithms need years of public scrutiny. An algorithm that has not been independently analyzed offers no meaningful security assurance, regardless of what physics terminology is attached to the marketing.
“Can you provide a peer-reviewed paper describing the security proof?” A genuine quantum or post-quantum security system will have a formal security proof under a specified threat model. If none exists, the security claim is unsubstantiated.
Quantum entanglement is real, and its security applications through QKD protocols like E91 are grounded in rigorous physics. But the security value of entanglement comes from physical properties that Bell’s theorem proves cannot exist in classical systems. “Simulating” entanglement on a classical chip and claiming quantum security properties is like simulating a vault door on a screen and claiming your building is secure.
If a product works, it works because of whatever classical algorithm it actually runs, not because of simulated quantum physics. I’d suggest evaluating it on those terms instead.
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