In the previous module, you learned about quantum superposition - that particles can exist in multiple states at the same time. In this module, you will be introduced to the concept of quantum entanglement - another strange quantum property that quantum computing will harness in order to deliver processing power unheard of in classical computers.

Entanglement describes the relationship that exists between two or more particles that interact in a way that makes it impossible to describe each particle independently. Rather, measurements of the particles reveal correlations, and as such the particles must always be described as a quantum state of the whole system.

Get started by reading our EPiQC zine about Entanglement!


In this video, we imagine that a quantum computer is choosing between the notes of Mary Had a Little Lamb and Twinkle, Twinkle, Little Star in order to illustrate the principles of quantum superposition and entanglement. We revisit this video - also a part of the collection of superposition resources - this time with a focus on entanglement.

What can Schrödinger's cat teach us about quantum mechanics? - Josh Samani

What happens when the laws that govern the world around us no longer apply? In this short video, the classic Schrodinger’s cat thought experiment is used to demonstrate the strange phenomenon of quantum entanglement.

Einstein’s brilliant mistake: Entangled States - Chad Orzel (Ted-Ed)

This video discusses the importance of Einstein, Podolsky, and Rosen’s 1935 EPR paper that - while incorrect - inspired physicists for years to come as they worked to understand the relationship between indeterminate states of entangled particles.
Read more about The Einstein-Podolsky-Rosen Argument in Quantum Theory.

Quantum Entanglement (IBM Q Research videos)

In this video, an IBM quantum computing researcher gives a brief discussion of quantum entanglement and its role in quantum computing.

What’s so special about entangled states anyway? (Quantum Computing for the Determined)

Become acquainted with the math describing quantum states and the two-qubit notation used for entangled qubits. A brief discussion of the role of entanglement in the processing power of quantum computers is included.  

More than one qubit (quantum Cryptography - delft)

This video discusses how to represent the quantum state of qubits. Examples are provided for each of the following two-qubit states: two qubits in equal superposition, the EPR pair, and two qubits that are not entangled.