____Cryogenic___temperatures_______.pptx

Cryogenic temperature in Quantum computing using cryo-CMOS

1. Cryogenic Temperatures

2. What is Cryogenic Temperatures? ‘ Kryos ’ has its Greek origin, meaning cold and frost. Extremely low temperatures. Typically range: below 123K (-150°C). Commonly used gases in their liquid form : Liquid nitrogen(LN2): 77K (-196°C) Liquid Helium(LH2): 4.2K (-269°C) Liquid Hydrogen(H2(l)): 20K (-253°C)

3. Applications and Industries Using cryogenics Low-power circuits Astronomy High performance computing Spacecraft operation Image sensors Quantum Computing

4. Scaling Challenges in Quantum Computing Qubits are the fundamental components of quantum computers. Commercial quantum computers rely on the bulky and unscalable instruments at RT to control ~ 20 qubits , posing a scaling challenge. Scaling Bottleneck : performance and scalability are constrained as the number of qubits increases . Solution : cryo-CMOS technology

5. Quantum Processor and Classical Controller Configuration Disadvantages : interconnections system size reliability Fig. 1. Quantum processor and classical controller connected in a control/readout configuration.

6. Cryo-CMOS Technology Cryo-CMOS is a CMOS technology that operates at deep cryogenic temperatures (below 77K) for quantum computing applications . Cryo-CMOS is crucial for qubit control and readout in quantum computers. Advantages : Less cabling- reduction of wire resistance Scalability Reliability Cost-Effective reduction of leakage current Fig. 2. Block diagram of the proposed cryo-CMOS controller for the control and readout of qubits

7. Impact on device and circuit performance Cryogenic environments heavily alter device behavior including various changes to main device parameters: Threshold voltage Effective mobility Sub-threshold slope

8. Threshold Voltage Threshold voltage, , is the minimum required to create a conductive path between the source and drain terminals of a MOSFET. This effect results from two reasons: Band-gap widening Incomplete ionization , also known as freeze-out Increasing in can be beneficial in reducing leakage currents .   Conduction band Valence band   Conduction band Valence band    

9. Threshold Voltage Fig. 3. Change of threshold voltage for temperatures across various technology nodes.

10.   The free carrier mobility, , defined as the average drift velocity in unit electric field. Enhanced mobility improves the drive current and switching speed of transistors, resulting in faster and more efficient electronic circuits. Main causes: Coulomb scattering ( dominant at low temperatures ) Phonon scattering- ( dominant at RT, high temperatures ) Surface roughness scatterings   Effective Mobility Fig. 4. Main scattering mechanisms as a function of temperature and inversion charge for MOSFETs.

11. Subthreshold Slope M easure s how effectively a transistor switches from off to on . Defined as the gate voltage change needed to increase the drain current by one decade, order of magnitude in the subthreshold region.               Fig. 5. Subthreshold Slope over temperature across various technology nodes.  

12. I on /I off Ratio / ratio holds valuable data about the transistor’s behavior, since it is the result of all cryogenic phenomena: threshold voltage increase, subthreshold voltage degradation and enhanced carrier mobility. The SS defines the voltage quantity must add/remove in order to increase/decrease the current by one order-of-magnitude.     Fig. 6. / ratio over temperature across various technology nodes.  

13. Challenges of Cryo-CMOS Device Models Design Tools Full-System Optimization

14. Conclusion