In classical circuit theory we have 4 fundamental circuit variables: the current, the voltage, charge, and flux linkage.

We can combine these variables in six pairwise relations, five of these relations are well known to us.

The first two pairs define the voltage and the current where the voltage is the rate of change in the flux linkage and the current is the rate of change in the charge.

The other three pairs define the fundamental circuit elements, we have the resistor which relates the current with the voltage, the capacitor which relate the voltage with the charge ,and the inductor which relate the current with the flux linkage.

These elements are called fundamentals because we cannot produce their behavior with other fundamental elements.

This leaves one relation ,which is the relation between the flux and the charge .

In 1971, a University of California, Berkeley, engineer predicted that there should be a fourth element in order to fill this gab .that element is what we’re going to talk about today!

You’re listening to techwise podcast coming to you by the IEEE UOT student branch and here we talk about science and technology from different fields, lets start!

an IEEE SENIOR MEMBER leon chua  predicted the existence of a fourth element called the memory resistor. Such a device, he figured, would provide a similar relationship between magnetic flux and charge that a resistor gives between voltage and current. In practice, that would mean it acted like a resistor whose value could vary according to the current passing through it and which would remember that value even after the current disappeared.

The reason that the memristor is different from the other fundamental circuit elements is that, unlike them, it kinda carries a memory of its past. When you turn off the voltage to the circuit, the memristor still remembers how much was applied before and for how long. That's an effect that can't be duplicated by any circuit combination of resistors, capacitors, and inductors, which is why the memristor qualifies as a fundamental circuit element.

You can think of it as a pipe that water runs through The width of the pipe is like the resistance of the flow of current ,the current here is the flowing water, which means the narrower the pipe, the greater the resistance. Normal resistors have an unchanging pipe size. A memristor, on the other hand, changes the amount of water that gets through. If the water goes in one direction, the pipe gets larger (less resistive). If it goes in the other direction, the pipe gets smaller (more resistive). And the memristor remembers .like When the water flow is turned off, the pipe size does not change.

Such a mechanism could technically be replicated using transistors and capacitors, but it takes a lot of transistors and capacitors to do the job of a single memristor.

for many decades it remained unobserved just hypothetical device.until  it was identified in HP labs in 2008 .where they found an ideal memristor in titanium dioxide . Like silicon, titanium dioxide is a semiconductor, and in its pure state it is highly resistive. However, it can be doped with other elements to make it very conductive. In TiO 2 , the dopants don't stay stationary in a high electric field; they tend to drift in the direction of the current. Such mobility is poison to a transistor, but it turns out that's exactly what makes a memristor work. 

In April 2022 scientists in Austria and Italy have developed a quantum version of the memristor.

quantum memristor that relies on a stream of photons existing in superpositions has been developed, where each single photon can travel down two separate paths laser-written onto glass

Normally, memristive behavior and quantum effects are not expected to coexist, Memristors are devices that essentially work by measuring the data flowing within them, but quantum effects are infamously fragile when it comes to any outside interference such as measurements. The researchers overcame this apparent contradiction by engineering interactions within their device to be strong enough to enable memristivity but weak enough to preserve quantum behavior.

These quantum memristors could lead to quantum neuromorphiccomputers

That’s a big word so let’s take it step by step 

Quantum computers rely on how the universe becomes a fuzzy place at its very smallest levels. For example, atoms, photons, and other building blocks of the cosmos can exist in states of flux known as superpositions, meaning they can essentially be located in two or more places at once, or spin in two opposite directions at the same time.

and neuromorphic computers which area very-large-scale integration systems to mimic neuro-biological architectures present in the nervous system.

Memristors have a Nano scale dimensions,low power consumption,and non-volatile memory ,these properties makes them suitable for many applications like computer memory ,programmable circuits and neuromorphic circuits 

In theory, memristors can act like artificial neurons capable of both computing and storing data. researchers have suggested that neuromorphic computers built using memristors would perform well at running neural networks, which are machine-learning systems that use synthetic versions of synapses and neurons to mimic the process of learning in the human brain.

, i read this quote that I think I kinda fitting for this episode ,I’s by Robert Heinlein a American science fiction author her wrote “One man’s “magic” is another man’s engineering. “Supernatural” is a null word.

And that’s all the time we have for now .Thank you all for listening and have a good day.