We propose a new method, "counter-factual" carving, that uses the "no-jump" evolution of a probe to generate entangled many-body states of high fidelity. The probe is coupled to a target ensemble of qubits and engineered to exponentially decay at a rate depending on the target collective spin, such that post-selecting on observing no probe decay precisely removes select faster-decaying spin components. When probe and $N$ -qubit target interact via a cavity mode of cooperativity $C$ , counter-factual carving generates entangled states with infidelities of $e^{-C/N}$ , an exponential improvement over previous carving schemes. Counter-factual carving can generate complex entangled states for applications in quantum metrology and quantum computing.We propose a new method, "counter-factual" carving, that uses the "no-jump" evolution of a probe to generate entangled many-body states of high fidelity. The probe is coupled to a target ensemble of qubits and engineered to exponentially decay at a rate depending on the target collective spin, such that post-selecting on observing no probe decay precisely removes select faster-decaying spin components. When probe and $N$-qubit target interact via a cavity mode of cooperativity $C$, counter-factual carving generates entangled states with infidelities of $e^{-C/N}$, an exponential improvement over previous carving schemes. Counter-factual carving can generate complex entangled states for applications in quantum metrology and quantum computing.

arXiv:2401.11407Jan 21, 20240 citations

Carving entangled multiparticle states with exponentially improved fidelity

Joshua Ramette, Josiah Sinclair, Zeyang Li +1 more

We propose a method that uses the ``no-jump'' evolution of a probe to generate entangled multiparticle states of high fidelity. The probe is coupled to a target ensemble of qubits and engineered to exponentially decay at a rate depending on the target collective spin, such that postselecting on observing no probe decay precisely removes select faster-decaying spin components. When a probe and $N$ -qubit target interact via a cavity mode of cooperativity $C$ , our procedure generates entangled states with infidelities of ${e}^{\ensuremath{-}C/N}$, an exponential improvement over previous carving schemes. This scheme, which we call ``counterfactual'' carving, can generate complex entangled states for applications in quantum metrology and quantum computing.We propose a method that uses the ``no-jump'' evolution of a probe to generate entangled multiparticle states of high fidelity. The probe is coupled to a target ensemble of qubits and engineered to exponentially decay at a rate depending on the target collective spin, such that postselecting on observing no probe decay precisely removes select faster-decaying spin components. When a probe and $N$-qubit target interact via a cavity mode of cooperativity $C$, our procedure generates entangled states with infidelities of ${e}^{\ensuremath{-}C/N}$, an exponential improvement over previous carving schemes. This scheme, which we call ``counterfactual'' carving, can generate complex entangled states for applications in quantum metrology and quantum computing.

Physical Review AMay 14, 20253 citations

Untangling Entanglement

ScienceFeb 5, 20040 citations

Untangling Entanglement

Peter Mark Ainsworth

Foundations of PhysicsJan 5, 20073 citations

Efficient and High-Fidelity Entanglement in Cavity QED without High Cooperativity

S. Goswami, C.-H. Chien, N. Sinclair +4 more

The so-called state-carving protocol generates high-fidelity entangled states at an atom-cavity interface without requiring high cavity cooperativity. However, this protocol is limited to 50% efficiency, which restricts its applicability. We propose a simple modification to the state-carving protocol to achieve efficient entanglement generation, with unit probability in principle. Unlike previous two-photon schemes, ours employs only one photon which interacts with the atoms twice-avoiding separate photon detections which causes irrecoverable probability loss. We present a detailed description and performance evaluation of our protocol under nonideal conditions. High fidelity of 0.999 can be achieved with cavity cooperativity of only 34. Efficient state carving paves the way for large-scale entanglement generation at cavity interfaces for modular quantum computing, quantum repeaters, and creating arbitrary shaped atomic graph states, essential for one-way quantum computing.The so-called state-carving protocol generates high-fidelity entangled states at an atom-cavity interface without requiring high cavity cooperativity. However, this protocol is limited to 50% efficiency, which restricts its applicability. We propose a simple modification to the state-carving protocol to achieve efficient entanglement generation, with unit probability in principle. Unlike previous two-photon schemes, ours employs only one photon which interacts with the atoms twice-avoiding separate photon detections which causes irrecoverable probability loss. We present a detailed description and performance evaluation of our protocol under nonideal conditions. High fidelity of 0.999 can be achieved with cavity cooperativity of only 34. Efficient state carving paves the way for large-scale entanglement generation at cavity interfaces for modular quantum computing, quantum repeaters, and creating arbitrary shaped atomic graph states, essential for one-way quantum computing.

arXiv:2505.02702Physical Review LettersDec 9, 20251 citation

N

-qubit target interact via a cavity mode of cooperativity

C

, counter-factual carving generates entangled states with infidelities of

e^{-C/N}

, an exponential improvement over previous carving schemes. Counter-factual carving can generate complex entangled states for applications in quantum metrology and quantum computing.

N

-qubit target interact via a cavity mode of cooperativity

C

, our procedure generates entangled states with infidelities of ${e}^{\ensuremath{-}C/N}$, an exponential improvement over previous carving schemes. This scheme, which we call ``counterfactual'' carving, can generate complex entangled states for applications in quantum metrology and quantum computing.