Hi!

Stefan Krastanov
University of Massachusetts Amherst

Research

Room-temp optical quantum computing¹
  1. Room-temperature photonic logical qubits via second-order nonlinearities
Room-temp optical quantum computing¹
Near-term² photonic hardware and accelerators for classical computation³
  1. Room-temperature photonic logical qubits via second-order nonlinearities
  2. Controlled-Phase Gate by Dynamic Coupling of Photons to a Two-Level Emitter
  3. All-Photonic Artificial Neural Network Processor Via Non-linear Optics
Room-temp optical quantum computing¹
Near-term² photonic hardware and accelerators for classical computation³
Control⁴ and networking⁵ of microwave devices
  1. Room-temperature photonic logical qubits via second-order nonlinearities
  2. Controlled-Phase Gate by Dynamic Coupling of Photons to a Two-Level Emitter
  3. All-Photonic Artificial Neural Network Processor Via Non-linear Optics
  4. Universal control of an oscillator with dispersive coupling to a qubit
  5. Optically-Heralded Entanglement of Superconducting Systems in Quantum Networks
Room-temp optical quantum computing¹
Near-term² photonic hardware and accelerators for classical computation³
Control⁴ and networking⁵ of microwave devices
Spin-mechanics interfaces⁶
  1. Room-temperature photonic logical qubits via second-order nonlinearities
  2. Controlled-Phase Gate by Dynamic Coupling of Photons to a Two-Level Emitter
  3. All-Photonic Artificial Neural Network Processor Via Non-linear Optics
  4. Universal control of an oscillator with dispersive coupling to a qubit
  5. Optically-Heralded Entanglement of Superconducting Systems in Quantum Networks
  6. A spin-optomechanical quantum interface [...]
Room-temp optical quantum computing¹
Near-term² photonic hardware and accelerators for classical computation³
Control⁴ and networking⁵ of microwave devices
Spin-mechanics interfaces⁶
Learning hardware parameters⁷⁸
  1. Room-temperature photonic logical qubits via second-order nonlinearities
  2. Controlled-Phase Gate by Dynamic Coupling of Photons to a Two-Level Emitter
  3. All-Photonic Artificial Neural Network Processor Via Non-linear OpticsPRApp 2024
  4. Universal control of an oscillator with dispersive coupling to a qubit
  5. Optically-Heralded Entanglement of Superconducting Systems in Quantum Networks
  6. A spin-optomechanical quantum interface [...]
  7. Stochastic estimation of dynamical variables
  8. Unboxing Quantum Black Box Models [...]

Quantum Networking

Hardware design and modeling

Entanglement distillation

Modular computation

Network control protocols (CQN)

Entanglement Purification

Optimized circuits for purification¹, better than any known circuits.
  1. Krastanov et al.
    Optimized Entanglement Purification
  2. Jansen et al.
    Enumerating all bilocal Clifford distillation protocols through symmetry reduction
  3. Addala et al.
    Faster-than-Clifford simulations of entanglement purification circuits and their full-stack optimization
  4. Wang et al.
    GHZ-Preserving Gates and Optimized Distillation Circuits
  5. Wang et al.
    Graph-state Optimized Distillation

Compilation for modular MBQC

  1. Quantum Hamlets: Distributed Compilation of Large Algorithmic Graph States

Error Correction

Silly ML decoders before they were cool

Bosonic ECC

Single-shot Stabilizer Codes

Room-temperature ECC Repeater

  1. Room-Temperature Photonic Logical Qubits via Second-Order Nonlinearities

Record-breaking Single-shot Codes

  1. Multivariate Multicycle Codes for Complete Single-Shot Decoding

Tool Building

early history ;)

Core contributor to SymPy;
drive-by PRs to the rest of the ecosystem;
Jupyter used to be just an ipython plugin

Most sophisticated Clifford algebra simulator

QuantumClifford.jl

Multiplying two 1 gigaqubit Paulis in 32 ms.

GPU acceleration, Pauli Frames, the usual

QuantumClifford.jl

As an "algebra" tool: random states, gate enumeration, canonicalization, partial traces, projections, group theory tool...

QuantumClifford.jl

As a "circuit simulation" tool: Monte Carlo, Pauli frames, and perturbative expansions.

QuantumClifford.jl

              Dict{CircuitStatus, Num} with 3 entries:
                failure       => 4e*((1 - 3e)^3)
                false_success => 6e*((1 - 3e)^3)
                true_success  => (1 - 3e)^4 + 2e*((1 - 3e)^3)
QuantumClifford.jl

Various weakly non-Clifford methods:

  • $\sum \alpha_i |\psi_{i}^{\text{STAB}}\rangle$
  • $\sum p_i\ U^\text{DESTAB}_i \rho^{\text{STAB}} U^{\text{DESTAB}\dagger}_i$
  • $U^{\text{Cliff}} |\text{MPS}\rangle$

Faster-than-Clifford Bell Pair circuits

BPGates.jl
Time to perform a pair of CNOT gates, depending on formalism
Symbolic description of quantum logic
Declarative noise models
Translation to many simulator backends
Discrete event scheduler
High-level lego-like interface

Being deployed for the virtual testbeds at NSF's CQN (ERC) and AspenNet (NQVL).

QuantumSymbolics.jl


              julia> Z₁
              |Z₁⟩
            

              julia> ( Z₁⊗X₂+Y₁⊗Y₁ ) / √2
              0.707 (|Y₁⟩|Y₁⟩+|Z₁⟩|X₂⟩)

Symbolic to Numeric Conversion


              julia> express( ( Z₁⊗X₂+Y₁⊗Y₁ ) / √2 )
              Ket(dim=4)
                basis: [Spin(1/2) ⊗ Spin(1/2)]
                 0.8535533905932736 + 0.0im
                                0.0 + 0.3535533905932737im
               -0.49999999999999994 + 0.3535533905932737im
                -0.3535533905932737 + 0.0im
            

              julia> express( Y₁⊗Y₂, CliffordRepr() )
              Rank 2 stabilizer
              + Z_
              + _Z
              ════
              + Y_
              - _Y
              ════

With `express` interfaces into (and between)

  • Stabilizer formalism (QuantumClifford.jl)
  • State vectors (QuantumOptics.jl and QuantumToolbox.jl)
  • Gaussian (Symplectic) states (Gabs.jl)

And other tools we support

  • WaveguideQED.jl
  • BPGates.jl
  • a variety of low-rank methods in QuantumClifford.jl

Waveguide Quantum Electrodynamics

WaveguideQED.jl
Quantum wavepacket reflected from a cavity

Caretaker Duties

QuantumOptics.jl, ResumableFunctions.jl, Graphs.jl

Outreach & Community Building

Summer of Code

Managed ~20 junior contributors (undergrad student jobs, REUs, summer of code, CQN interns, etc).
About 10k$ bounty & summer project budget per year and the occasional larger subcontracts.

QNumerics Summer School

STEM Outreach

The Spinwheel
spinwearables.com
The Qbead
qbead.org