New Technique: Layerwise Richardson Extrapolation

[purva-thakre]

Add technique introduced in https://arxiv.org/abs/2402.04000

Link to the code: https://github.com/unitaryfund/research/tree/8c3ff3f46bb9fe91941fe073cb903a30f65b13e1/lre

This technique is different from the layerwise noise scaling technique in mitiq/zne/scaling/layer_scaling.py

mitiq/mitiq/zne/scaling/layer_scaling.py

Lines 21 to 23 in 244d52a

	def layer_folding(
	circuit: cirq.Circuit, layers_to_fold: List[int]
	) -> cirq.Circuit:

• RFC: Layerwise Richardson Extrapolation (LRE) #2224
• LRE Functions: Noise Scaling #2307
• Multivariate inference for LRE #2372
• Executors for LRE #2370
• User's Guide for LRE #2371
• LRE Tutorials #2373
• Make LRE compatible with non-cirq circuits #2416
• Make sure LRE executors work with observables #2513