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arXiv:2602.15080 · Modern Physics Letters A

Geometry of Quantum Logic Gates

M. W. AlMasri

quant-phSubmitted Feb 16, 2026• Announced Feb 17, 2026• 0 citations
v1 · Feb 16, 2026v2 · Apr 13, 2026
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Abstract

In this work, we investigate the geometry of quantum logic gates within the holomorphic representation of quantum mechanics. We begin by embedding the physical qubit subspace into the space of holomorphic functions that are homogeneous of degree one in each Schwinger boson pair $(z_{a_{j}}, z_{b_{j}})$. Within this framework, we derive explicit closed-form differential operator representations for a universal set of quantum gates--including the Pauli operators, Hadamard, CNOT, CZ, and SWAP--and demonstrate that they preserve the physical subspace exactly. Restricting to unit-magnitude variables ($|z| = 1$) reveals a toroidal space $\mathbb{T}^{2N}$, on which quantum gates act as canonical transformations: Pauli operators generate Hamiltonian flows, the Hadamard gate induces a nonlinear automorphism, and entangling gates produce correlated diffeomorphisms that couple distinct toroidal factors. Beyond the torus, the full Segal--Bargmann space carries a natural Kaehler geometry that governs amplitude dynamics. Entanglement is geometrically characterized via the Segre embedding into complex projective space, while topological protection arises from the $U(1)^{N}$ fiber bundle structure associated with the Jordan--Schwinger constraint.

Journal reference
Mod. Phys. Lett. A 41 (25), 2650141 (2026)
DOI
10.1142/S0217732326501415
Comments
8 pages

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In this work, we investigate the geometry of quantum logic gates within the holomorphic representation of quantum mechanics. We begin by embedding the physical qubit subspace into the space of holomorphic functions that are homogeneous of degree one in each Schwinger boson pair (zaj,zbj)(z_{a_{j}}, z_{b_{j}})(zaj​​,zbj​​). Within this framework, we derive explicit closed-form differential operator representations for a universal set of quantum gates--including the Pauli operators, Hadamard, CNOT, CZ, and SWAP--and demonstrate that they preserve the physical subspace exactly. Restricting to unit-magnitude variables (∣z∣=1|z| = 1∣z∣=1) reveals a toroidal space T2N\mathbb{T}^{2N}T2N, on which quantum gates act as canonical transformations: Pauli operators generate Hamiltonian flows, the Hadamard gate induces a nonlinear automorphism, and entangling gates produce correlated diffeomorphisms that couple distinct toroidal factors. Beyond the torus, the full Segal--Bargmann space carries a natural Kaehler geometry that governs amplitude dynamics. Entanglement is geometrically characterized via the Segre embedding into complex projective space, while topological protection arises from the U(1)NU(1)^{N}U(1)N fiber bundle structure associated with the Jordan--Schwinger constraint.
We develop a holomorphic representation of quantum error correction codes (QECCs) within the Segal--Bargmann space. By encoding qubits into Schwinger boson modes (zaj,zbj)(z_{a_j}, z_{b_j})(zaj​​,zbj​​) subject to a degree-one homogeneity constraint, we derive closed-form differential operator representations for stabilizers, syndrome extraction, and recovery for fundamental codes (three-, five-, seven-, and nine-qubit codes). Quantum errors are characterized as holomorphic perturbations violating this constraint, while syndrome measurement projects onto eigenspaces of commuting differential operators. Restricting to unit-magnitude variables (∣z∣=1|z|=1∣z∣=1) reveals a toroidal space $\T^{2n}$ where error syndromes manifest as discrete translations in winding number space Z2n\Z^{2n}Z2n, and recovery acts as Hamiltonian flows restoring the winding configuration. In the full Segal--Bargmann space, the code space is a holomorphic submanifold of $\CP^{2^n-1}$, with correctable errors as transverse normal directions. Consequently, the Knill--Laflamme condition becomes a Fubini--Study orthogonality condition between the code submanifold and its error-translated images. Topological protection emerges from the U(1)nU(1)^nU(1)n fiber bundle structure: global phase noise along fibers is unobservable, while base-space errors require active correction. Finally, we establish a path-integral formulation for semiclassical error correction dynamics and show that geometric entanglement via the Segre embedding naturally quantifies code distance. This framework unifies algebraic, geometric, and topological perspectives on fault-tolerant quantum protocols.
Abstract We develop a wave mechanics formalism for qubit geometry using holomorphic functions and Möbius transformations, providing a geometric perspective on quantum computation. This framework extends the standard Hilbert space description, offering a natural interpretation of standard quantum gates on the Riemann sphere that is examined through their Möbius action on holomorphic wavefunction. These wavefunctions emerge via a quantization process, with the Riemann sphere serving as the classical phase space of the qubit geometry. We quantize this space using Isham’s canonical group quantization with holomorphic polarization, yielding holomorphic wavefunctions and spin angular momentum operators that recover the standard SU (2) algebra with interesting geometric properties. Such properties reveal how geometric transformations induce quantum logic gates on the Riemann sphere, providing a novel perspective on quantum information processing. This result provides a new direction for exploring quantum computation through Isham’s canonical group quantization and its holomorphic polarization method.
A quantum gate is the quantum analog of the classical logic gate of digital computers. It is a basic structural unit of a quantum circuit which operates on a small number of qubits to deliver a predefined output. A quantum circuit is a graphical representation of the sequence of the quantum gates used and the measurements performed in a quantum computation. Various quantum logic gates, namely, the Hadamard, T phase, NOT, Pauli-X, controlled NOT (CNOT), controlled-Z, SWAP and controlled phase gates as well as higher-level Toffoli and Fredkin gates are described. Conventions of reading quantum circuit diagrams are explained. Operation of a quantum full adder consisting of registers and gates is discussed, elaborating the role of the NOT gate, the sum calculation with CNOTgates and the carry C-out calculation with Toffoli gates. A primary tool used for performing arithmetic operations on a quantum computer is the quantum Fourier transform (QFT). The QFT adder and multiplier circuits are presented.
We study bosonic quantum computations using the Segal-Bargmann representation of quantum states. We argue that this holomorphic representation is a natural one which not only gives a canonical description of bosonic quantum computing using basic elements of complex analysis but also provides a unifying picture which delineates the boundary between discrete- and continuous-variable quantum information theory. Using this representation, we show that the evolution of a single bosonic mode under a Gaussian Hamiltonian can be described as an integrable dynamical system of classical Calogero-Moser particles corresponding to the zeros of the holomorphic function, together with a conformal evolution of Gaussian parameters. We explain that the Calogero-Moser dynamics is due to unique features of bosonic Hilbert spaces such as squeezing. We then generalize the properties of this holomorphic representation to the multimode case, deriving a non-Gaussian hierarchy of quantum states and relating entanglement to factorization properties of holomorphic functions. Finally, we apply this formalism to discrete- and continuous- variable quantum measurements and obtain a classification of subuniversal models that are generalizations of Boson Sampling and Gaussian quantum computing.
This work introduces a complete and self-consistent framework for quantum computation within the domain of real-valued quantum mechanics. Standard quantum computation is predicated on the manipulation of states in a complex Hilbert space, where a complex phase is a critical resource. We demonstrate that this complex structure is not fundamental but can be fully reproduced by a real-operator algebra. Our formalism is built upon a rigorous algebraic isomorphism between the imaginary unit i and the temporal Hilbert transform operator Ht\mathcal{H}_tHt​, which acts as a physical generator of phase. Leveraging this isomorphism, we systematically redefine the fundamental quantum logic gates-including the Pauli, Hadamard, phase rotation, and CNOT gates-entirely within a real operator algebra. We prove that each gate's action on a real-valued qubit state representation is mathematically and operationally equivalent to its conventional complex counterpart. The Pauli-Y, phase, and controlled-phase gates, which are intrinsically complex in the standard model, are shown to correspond to real-operator matrices involving the Hilbert transform. This formulation provides a physically grounded interpretation of quantum logic, where abstract phase manipulation corresponds to the application of a concrete, albeit non-local, integral transform. We demonstrate how this framework correctly reproduces the generation of quantum entanglement and establishes a consistent measurement theory via an Analytic Born Rule in Unified Quantum Mechanics. This work solidifies the viability of a complete real-valued model for quantum information processing and suggests new paradigms for the physical implementation of quantum hardware.
We extend the framework of the Three-Dimensional Complex Necessity (3DCN) principle to quantum information theory, demonstrating that the complex probability amplitudes of qubits are emergent manifestations of real, restricted geometric rotations on a 2D transverse phase space substrate. Conventionally, a quantum bit (qubit) is axiomatically formulated on a complex Hilbert space, leaving its state vulnerable to environmental decoherence. By replacing the algebraic primitive i with the coordinate-covariant universal complex structure tensor J_U satisfying J_U^2 = -I derived from oriented 3D geometry, we construct a purely real-geometric formulation of quantum computing. We mathematically prove that the canonical Bloch sphere can be mapped onto a real 4-dimensional physical phase space reduced by first-class constraints. Under this formulation, unitary quantum gates (such as Hadamard and CNOT) are executed via real spatial transformations, while the topological Ward identity governing the interaction locking mechanism provides a built-in geometric defense against phase decoherence without requiring active quantum error correction protocols.